Rockwood & Green’s Fractures in Adults
6th Edition

Chapter 51
Dislocations and Fracture-Dislocations of the Knee
Robert C. Schenck Jr
James P. Stannard
Daniel C. Wascher
The treatment of knee injuries requires a unique understanding of anatomy, biomechanics, function, and injury mechanisms that crosses over areas of expertise in sports medicine and hard orthopaedic trauma. The examination and diagnosis of the knee have undergone numerous refinements and technological advances in the past decades. The broad range of treatment options for the knee has also seen recent advancements. This chapter will build upon the preceding editions in an attempt to advance the scope and review the current knowledge base and accepted treatment practices for severe knee injuries, including knee dislocations, fracture-dislocations, and dislocations of the proximal tibiofibular joint.
One’s understanding of knee anatomy is often as varied as one’s clinical experience. Although arthroscopy has been a tremendous technological advancement, the infrequency of open procedures has limited the younger orthopaedist’s exposure to the anatomy of the posterolateral and posteromedial corners of the knee. With complex, multiple ligament injuries of the knee, primary open procedures such as posterolateral corner repairs

or reconstructions are frequently indicated, and a thorough understanding of knee anatomy is essential but less well appreciated.
The impact of any injury to the knee is best defined by its effect on knee function, as described by Lorizou and also emphasized by Losee (1,2). Clinical knee evaluation requires a careful history and physical examination but just as importantly must also include a determination of function (3). The knee is easily evaluated for function by simple observation of the patient’s gait. Ideally, evaluation of function should occur after the history and before the physical examination, depending upon the acuity and severity of injury. Simple evaluation of functional integrity of the extensor mechanism is a good example where treatment changes depending upon the ability of a patient to perform a straight-leg raise, thus differentiating a complete from a partial injury of the extensor mechanism. With severe or multiple orthopaedic injuries, evaluation of function, especially gait, may be difficult if not impossible; however, understanding the concept of function placed between history and physical examination is extremely important in the evaluation of the injured knee.
Furthermore, the knee is the classic example for careful functional evaluation of ligaments. The examination of the knee is well defined and the current knowledge base of functional clinical tests probably exceeds that of any other joint in the body. With the advent of MRI, clinical examination may wrongly take a secondary position to an easily obtained radiographic study or even arthroscopy. Clinical examination for functional integrity of the knee ligaments is critical to establish a diagnosis of which ligaments are functionally intact. Furthermore, examination under anesthesia (EUA) is invaluable in the diagnosis and treatment of the severely injured knee. Use of an EUA in sports injuries, multiple trauma, and equivocal examinations is often overlooked but no less important than arthroscopy, MRI, CT, or open exploration of the joint. Treatment determination with pure knee ligament injuries is dependent upon the EUA and the presence or absence of physical findings of functional ligamentous integrity.
Unique Considerations
The knowledge base for treatment of the knee spans many levels of complexity in basic science (bone, hyaline, and meniscal cartilage, and ligamentous healing), rehabilitation, and basic surgical options of open or arthroscopic approaches. Furthermore, the numerous technological advancements in the surgical treatment of the knee can improve and quicken recovery. The complex decision regarding joint motion postoperatively depends upon a blend of experience, the repair techniques used, and the stability of repair/fixation of the injury. Although this chapter will not focus on chronic reconstructions of the knee, ligamentous reconstruction for acute or subacute injuries is well accepted and must be part of one’s decision making in treatment of the severely injured knee.
Treatment of knee trauma also requires specific knowledge of commonly associated injuries. Sports injuries are classically considered low-velocity injuries but can involve high-velocity patterns. Frequently it is the recognition of high-energy trauma in a sports injury that alerts the clinician to associated injuries. This continuum from a “sports” (low velocity or energy) to a “motor vehicular trauma” (high velocity or energy) mechanism is often overlooked, but with experience it is clearly an important differentiation for proper treatment of any knee injury. The associated vascular and neurologic injuries unique to the knee are extremely important, as delay in their diagnosis can have grave implications. Popliteal arterial injury, compartment syndrome of the leg, and peroneal nerve involvement are commonly seen and require prompt recognition and treatment. The frequent combination of joint surface fracture or contusion and ligamentous injury, as well as the distinction between midsubstance and avulsion ligament injuries, are common issues that determine appropriate treatment of the severely injured knee. The phenomenon of fracture-dislocation of the knee is also critical in directing appropriate treatment and will be discussed in detail in this chapter.
Associated conditions of the knee require specific consideration. Arthritis and arthrofibrosis (stiffness) of the knee have a significant impact on treatment decision making. Arthritis in the young or middle-aged adult is extremely difficult to manage, especially if osteotomy is not an option, such as when two of the three knee articular compartments are involved. In a young active patient, use of total joint arthroplasty in the treatment of arthritis carries a significant risk of failure or infection and has limited application in posttraumatic degenerative joint disease in the patient under 40 years of age (Fig. 51-1). Thus, arthritis is difficult to manage in knee injuries, especially if it involves all three compartments, and is best avoided if possible. Lastly, stiffness of the knee is a difficult complication that often becomes

permanent if not managed early and aggressively. Although ligamentous failure in posterior cruciate or posterolateral ligamentous injuries continues to occur, the more common complication of knee stiffness is often more functionally limiting than late knee instability. Avoidance of stiffness is very important in the successful treatment of the severely injured knee.
FIGURE 51-1 Medial compartment arthrosis evidenced by medial joint space narrowing in a 24-year-old man, 5 years after a complete knee dislocation with popliteal artery injury (KDIIIMCN).
Basic Anatomy and Biomechanics
The knee is formed by the femur, tibia, and patella. It consists of three partially separate compartments: patellofemoral, medial tibiofemoral, and lateral tibiofemoral (4,5,6). Although serving an important insertion point for the lateral ligaments of the knee, the fibular head does not articulate with the knee joint. Nonetheless, the knee joint capsule laterally extends distally superficial to the proximal fibula. The tibiofemoral compartments are the most complex and, combined with ligamentous interaction, allow transverse rotation of the tibia on the femur during knee flexion and extension. The articulation of the tibia and fibula is separate from the knee joint.
The femoral condyles are asymmetric in size and shape. The medial femoral condyle is approximately 1.7 cm longer than the lateral condyle in its outer circumference; the asymmetry in length produces axial rotation of the tibia on the femur during flexion and extension (4). The width of each individual condyle is similar, with the lateral being slightly wider than the medial when measured at the center of the intercondylar notch. In the sagittal axis of the knee, the lateral femoral condyle is longer or more anterior than the medial condyle. In the coronal or anterior-posterior (AP) plane, the medial femoral condyle projects further distally than the lateral condyle (5,6). When viewing the femur along its anatomic axis, this appearance becomes obvious. However, in normal weight-bearing alignment, the condyles appear equal in length. The parallel condylar surfaces are created by the mechanical axis configuration of the lower extremity. The weight-bearing axis is a straight line from the center of the femoral head (medial to the femoral axis) intersecting the center of the knee and ankle joints. Thus, the distal femoral joint line forms a six-degree angle to the long axis of the femoral shaft, creating physiologic valgus of the distal femoral joint line.
The tibial plateau joint surface is complex. The normal tibial articulation requires the menisci to provide congruity with the distal femoral condyles; in reality, the menisci should be considered tibial extensions. The menisci function to create conformity between the flat tibial and curved femoral surfaces. Biomechanically the menisci function to decrease the stress (force per unit area) concentration of tibiofemoral contact by increasing the surface area of contact between the tibia and femur during weight-bearing and range of motion (7,8). Without the menisci, the tibial and femoral hyaline surfaces carry similar forces but distributed over a smaller surface area, resulting in stress concentration (9,10). The medial plateau is nearly flat and has a larger surface area than the lateral plateau. The lateral plateau surface is slightly concave. Both plateaus have a 10-degree posterior inclination to the tibial shaft in the sagittal plane. Bordering the notch are the tibial spines (or tubercles), both medial and lateral, which, as bony elevations, function to stabilize the condyles from side-to-side motion. The interspinous area is void of hyaline cartilage, as are the insertion sites for the meniscal horns and cruciates. The cruciates insert in this intertubercular sulcus and not into the spines themselves (2,5,6,11,12,13).
Important landmarks of the knee include the medial and lateral femoral epicondyles (collateral ligament origins), the tibial (patellar tendon insertion) and Gerdy’s (iliotibial band insertion) tubercles, and the posteromedial border of the proximal tibia. The fibula and peroneal nerve are easily palpated and are important landmarks in any procedure about the lateral side of the knee.
The vascular supply about the knee is a complex anastomosis of two separate systems, the intrinsic and extrinsic networks. The intrinsic supply is an anastomotic ring made up of the articular, muscular branches and five geniculates (the superior-medial and lateral geniculates, the middle geniculate, and the inferior medial and lateral geniculates). The middle geniculate arises from the anterior aspect of the popliteal artery and enters the knee joint through the posterior oblique ligament supplying the cruciate ligaments and the contents of the notch. The medial and lateral superior geniculates wrap around the distal femur just proximal to the condyles. The inferior medial geniculate runs two fingerbreadths below the medial joint line. The inferior lateral geniculate courses along the lateral joint line adjacent to the lateral meniscus and must be considered in any approach involving the lateral aspect of the knee. The extrinsic system is made up of the descending genicular branch of the superficial femoral artery, the recurrent branch of the anterior tibial artery, and the descending branch of the lateral femoral circumflex artery (a branch of the profunda femoris) (5,6).
The anastomotic network provides for a rich blood supply to the skin overlying the knee and patella and allows for adequate vascularity even with subcutaneous dissection (Fig. 51-2). When raising flaps of skin in a surgical approach, the geniculate (intrinsic) supply to the skin can be interrupted but soft tissue viability is maintained due to the extrinsic system. When parallel incisions are used (such as parallel medial and lateral parapatellar incisions), the skin flaps are dependent upon the width of the superior and inferior vascular pedicles of the extrinsic system. Planning of such incisions to avoid skin bridge necrosis requires an appropriate width of at least 7 to 10 cm between incisions. When skin loss occurs, the defect must be covered, most frequently with a rotationplasty of the medial gastrocnemius muscle. The medial gastrocnemius flap (with careful dissection and proximal release) can cover skin defects that cross the midline of the knee (Fig. 51-3). The lateral gastrocnemius is a useful flap but is smaller than the medial flap and cannot be used to cover defects crossing the midline. Furthermore, it usually requires a peroneal nerve release.
Although the intrinsic/extrinsic systems provide adequate vascularity for superficial knee dissections, the anastomotic ring provides inadequate collateral flow to the lower leg when the

popliteal flow is disrupted. The recognition and diagnosis of such an arterial injury will be discussed in the section on knee dislocations.
FIGURE 51-2 The superficial vascular anastomotic ring of the anterior knee.
The nerve supply to the knee involves contributions of the sciatic (medial popliteal nerve) and the posterior division of the femoral nerve (saphenous nerve). The popliteal nerve courses through the popliteal fossa, enveloped in fat, and runs between the medial and lateral heads of the gastrocnemius. In the fossa, the popliteal artery crosses from medial to lateral with the vein interposed between the artery and nerve. The popliteal nerve gives off several muscular branches, articular branches, and the sural cutaneous nerve, which courses along the inner edge of the medial gastrocnemius. The lateral popliteal nerve courses over the lateral gastrocnemius, sending off a sural comminuting branch, and then becomes the peroneal nerve, winding around the neck of the fibula and branching into the musculocutaneous and anterior tibial nerves (5,6,13,14).
Muscle and Ligamentous Anatomy
The knee joint has a complex anatomic arrangement of muscular and ligamentous attachments. Separate from the welldescribed compartments of the leg, the knee is described as also having anterior, medial, lateral, and posterior compartments. Key to this description of compartmentalization is the concept of layers about the knee, which are useful in understanding the complex and varied anatomy of the posterolateral and posteromedial corners of the knee. The layer system is divided into three sections: I, II, and III. Layer I is a fascial layer and the most superficial layer. Simply put, layer I is uniform in describing the arciform layer anteriorly, sartorius fascia medially, and iliotibial band and biceps femoris fascia laterally (15). Layer II describes the patellar tendon, the superficial medial collateral ligament (MCL), and the fibular or lateral collateral ligament (LCL). Layer III is defined as joint capsule with its functional capsular thickenings including the posterior oblique and arcuate ligaments, the deep MCL, and the middle third of the lateral joint capsule. Simplistically, but accurately, level III includes all joint capsular structures but has multiple anatomic variations in thickness, creating distinct ligaments. Anteriorly the capsule is thin and adherent to the patellar tendon. Posterolaterally the capsular thickening is named the arcuate ligament (the posterior third of the capsule, laterally) and is thickened posteromedially as the posterior oblique ligament (POL) (the posterior third of the capsule medially) (Fig. 51-4) (15,16,17).
The posterior aspect of the knee includes the neurovascular structures, the medial and lateral gastrocnemius heads, the plantaris muscle, and the posterior knee joint capsule. The floor of the popliteal fossa is formed by the posterior femur, posterior

capsule, oblique popliteal ligament, and popliteus muscle. The neurovascular structures travel through the fossa between the medial and lateral gastrocnemius heads. The popliteal artery enters the fossa through the adductor magnus and runs in direct contact with the posterior oblique ligament. The popliteal vein enters the popliteal fossa on the lateral side of the artery, crossing superficially (between the artery and nerve) to lie medial to the artery in the distal aspect of the fossa. The posterior synovial cavity communicates in approximately 50% of persons with a popliteal bursa between the semimembranosus tendon and the medial head of the gastrocnemius. This bursa can become enlarged with chronic knee inflammation or intraarticular knee pathology (i.e., a Baker’s cyst).
FIGURE 51-3 A. Plain x-ray with chronic osteomyelitis of the proximal tibia after an open fracture-dislocation of knee. B. Debrided wound with exposed tibia and bony defect lateral to midline. C. Prepared medial gastrocnemius flap prior to rotation (the medial head can be split for added coverage if necessary). D. Split medial gastrocnemius rotation flap covering the proximal tibia.
The anterior and posterior cruciate ligaments provide anterior and posterior knee stability in the sagittal plane, respectively. The anterior cruciate ligament (ACL) originates posterolaterally in the femoral notch and inserts onto the tibial eminence. ACL integrity is determined best by the Lachman maneuver with the knee positioned in 25 degrees of flexion. The posterior cruciate ligament (PCL) originates in the anteromedial aspect of the femoral notch and inserts posteriorly on the tibia. The PCL is approximately twice as thick as the ACL and measures approximately 38 mm in length. It comprises two bundles, the anterolateral (anterior on the femur and lateral on the tibia) and the posteromedial (posterior on the femur and medial on the tibia). PCL integrity is best tested by the posterior drawer test.
Muscular Attachments
Comprehending the motor function about the knee is important to understand gait as well as dynamic knee joint stability. Although



the simplistic view of the knee as a hinge with extensor (quadriceps femoris muscle) and flexor (hamstring muscle) function is a useful start, the function of the quadriceps and hamstrings is different in gait. Function determines the muscular architecture, and muscle “form” is usually one of two types. Wide, bulky muscles (deltoid, gluteus maximus, quadriceps) function to create power and, specifically with the quadriceps muscle, to function for power or function in gait as a shock absorber. Long, narrow (gracile) muscles (gracilis, semitendinosus, biceps) function to change the velocity of a specific joint and, specifically with the hamstrings, to slow the leg for heel strike at the end of swing phase. Furthermore, the specific gait function of the quadriceps and hamstrings during walking is not to produce extension and flexion, respectively, but just the reverse. At heel strike, the quadriceps contracts eccentrically, allowing the knee to flex and in effect absorb impact energy (eg, when landing from a jump, the quadriceps provides controlled flexion of the knee). Likewise, the hamstring muscles fire eccentrically during swing phase to slow the leg (and foot) down in preparation for heel strike, in effect controlled extension of the knee. The gastrocnemius also has important functions in the gait cycle. As a strong knee flexor, it functions eccentrically to decelerate the leg and body for heel strike. Once in stance phase it controls knee flexion to prevent a back knee gait; finally, at toe-off, the gastrocnemius functions concentrically to push off in conjunction with the soleus. One must understand the gait or functional activity of these three muscle groups to correctly observe and interpret gait, as well as to prescribe rehabilitation following injury.
FIGURE 51-4 The lateral supporting structures of the knee. A. Lateral side of the knee with the skin and subcutaneous tissues removed. B. Cross-section of the knee at the joint level showing the lateral compartment structures. C. The ligamentous structures of the lateral knee after reflection of the iliotibial band. D. The deep ligamentous structures of the lateral knee and the corresponding capsular (layer III) ligaments.
The quadriceps is made up of four muscles with a common tendinous insertion on the patella. The rectus femoris crosses the hip joint, originating from the ilium to form the anterior portion of the quadriceps muscle tendon group. The vastus lateralis originates from the lateral femur along the linea aspera and the lateral intermuscular septum. The vastus lateralis has attachments to both the lateral patella and the iliotibial band, in effect indirectly inserting on the tibia. The vastus medialis originates from the proximal femur, inserting into the common tendon as well as the medial portion of the patella. The lower border of the vastus medialis originates from the tendon of the adductor magnus and has almost horizontal or transverse fibers inserting into the patella; it is termed the vastus medialis obliquus. The vastus intermedius arises from the femoral shaft and blends with the medialis musculature and tendinous insertion. The muscles form a trilaminar tendon, with the rectus anterior, the medialis, and the intermedius in the intermediate layer and the lateralis representing the deepest layer. Innervation of the four quadriceps muscles is from the femoral nerve.
The line of force of the quadriceps through the patella is not in a straight line with the patellar tendon. The patellar tendon inserts laterally on the tibia through the tibial tubercle. Furthermore, the quadriceps alignment along the femoral shaft produces a valgus angle of pull on the patella. Combined with the laterally positioned patellar tendon insertion, the quadriceps angle (Q angle) is formed from the anterior superior iliac spine through the patella and laterally on the tibial tubercle. The Q angle varies among persons and averages 10 to 20 degrees, generally being greater in females than in males. This valgus pull of the quadriceps creates a lateral vector on the patella that is countered by the higher lateral femoral condyle, the medial patellofemoral ligament, and the oblique fibers of the vastus medialis obliquus muscle.
The hamstring musculature is made up of the gracilis, semitendinosus, semimembranosus, and biceps femoris muscles. The medial side of the knee involves the semimembranosus insertions and the pes anserinus (the “goose foot” made up of the sartorius, gracilis, and semitendinosus). The sartorius muscle arises from the anterior superior iliac spine and runs down the front of the thigh with innervation from the femoral nerve. Its insertion is expansive as a fascial covering (layer I) surrounding the deeper insertions of the remaining two pes tendons. The gracilis muscle originates from the pubic arch and also runs medially in the thigh to insert approximately 4 cm below the joint line with innervation from the obturator nerve. The semitendinosus innervation sciatic nerve originates from the ischial tuberosity and travels in the thigh on the surface of the semimembranosus. The semitendinosus tendon inserts posterior to the gracilis on the medial tibia. The semimembranosus muscle originates from the ischial tuberosity via a long tendon and courses medially and deep to the biceps femoris, inserting on the posteromedial aspect of the tibial condyle. It provides a strong expansion posteriorly and medially to the knee, in effect continuing to form the posterior oblique ligament of the knee with condensations of layers II and III. Its innervation is the sciatic nerve. The biceps femoris arises in the form of two heads, the long head from the ischial tuberosity in common with the semitendinosus, and the short head from the linea aspera of the femur and lateral intermuscular septum. The innervation is dependent upon the muscle belly: the long head is via the sciatic nerve, the short head via the lateral popliteal nerve. Insertion of both muscle bellies is through a common tendon to the fibular head with expansions to the lateral tibia.
The gastrocnemius is composed of two muscle bellies, the medial and lateral heads. Both heads originate above the respective femoral condyle in the area of the distal femoral physis. The tendinous portions insert into the common tendon of the soleus to form the Achilles tendon. The plantaris muscle originates from the lateral supracondylar line and gives rise to a long narrow tendon running deep to the gastrocnemius. The gastrocnemius, soleus, and plantaris are innervated by the medial popliteal nerve. The popliteus has a tendinous origin at the lateral femoral condyle and inserts via a muscle belly distally onto the posterior surface of the tibia just above the soleal line. The popliteus tendon separates the lateral meniscus from the posterior joint capsule. Its function is not entirely defined, but it is thought to unlock the lateral tibial compartment in early flexion, produce roll-back of the lateral femur, and provide dynamic posterolateral stability to the knee joint in conjunction with the static stabilizers, the LCL, and the arcuate ligament. In its static function, the popliteus restricts posterior translation,

varus rotation, and external rotation of the tibia on the femur. Due to its oblique orientation on the tibia, the popliteus is also a dynamic restraint to tibial external rotation.
The tibiofibular joint comprises capsular, anterior, and posterior ligaments, which produce its stable articulation. The joint of the proximal tibiofibular articulation is either oblique or vertical and has little compensatory motion. Below the joint is an aperture in the interosseous membrane to allow passage of the anterior tibial vessels. The styloid of the proximal fibula has important insertion sites for the biceps femoris, the LCL, and the popliteofibular ligament.
Surgical Approaches to the Knee
With the development of arthroscopy, access to the knee joint is possible with increasingly smaller incisions. Nonetheless, early repair of multiple ligament injuries about the knee as well as associated fractures usually requires an open approach. Less frequently, an incision is required for arthrotomy for diagnostic purposes, as arthroscopy can commonly provide adequate joint access. Hence, incisions are used to approach the medial and lateral corners of the knee and tendon ruptures and more recently for access to the tibial insertion of the PCL (the PCL inlay technique). Commonly used open approaches include anterior, anteromedial, posteromedial, and posterolateral; a less common approach is straight posterior (18).
Restoring ligament function of the dislocated knee remains a challenge for the orthopaedic surgeon and requires skills that combine the subspecialty disciplines of both sports medicine and orthopaedic traumatology. As Meyers and Harvey noted in 1971, “It is.|.|. unlikely that any single physician personally cares for more than a few [knee dislocations] in a lifetime of practice” (19). Furthermore, access to trauma will determine one’s exposure to knee dislocations (20,21). Knee dislocations were considered a rare injury in the older published literature (19,21,22). However, numerous recent publications have noted that the frequency of diagnosis of knee dislocation has increased over the past several years. The reasons for the increasing diagnosis of knee dislocation are multifactorial and include increased awareness that many dislocations have already spontaneously reduced (and thus been previously unrecognized); increased awareness of the likelihood of dislocations associated with fractures of the lower extremity; and improvements in the trauma system, leading to increasing survival of seriously injured patients following blunt trauma, both sporting and motor vehicle trauma (23,24,25,26,27).
Furthermore, the incidence of knee dislocations is probably underreported. In the report by Wascher et al, a spontaneously reduced knee dislocation occurred in over 20% of patients; the incidence has been reported to be as high as 50% (20,21,22,23). Thus, one’s exposure to this injury type will depend on the practice environment as well as one’s level of suspicion in the injured patient. Most dislocations occur in multiply injured patients with high-energy trauma. It is easy to miss this diagnosis in a patient with multiple trauma because of the more obvious skeletal injuries. Unlike the clinician’s common exposure to ACL injuries, the relative rarity of knee dislocations and the lack of experience with combined ACL and PCL injuries add to the difficulty encountered in treating this problem (28). The potential combination of injury patterns (corner injuries, musculotendinous injuries, avulsions, popliteal arterial injury, and peroneal nerve injury), the association of multiple trauma, and the possibility of open injuries are some of the many difficulties encountered in the treatment of a knee dislocation.
Principles of Management
Mechanism of Injury
The mechanisms of injury in knee dislocations are varied and can occur in a low- or high-velocity setting (e.g., sporting or motor vehicle injury, respectively). The position of the knee and the exaggeration of motion result in ligament tearing. Exaggerated hyperextension is most common in both velocity mechanisms. A varus- or valgus-directed force in combination with hyperextension produces the variability in the collateral ligaments torn. Lastly, the knee positioned in flexion (most commonly 90 degrees while seated in a motor vehicle) with a posteriorly directed force (also in combination with either a varus or valgus force) is a common dislocation mechanism in high-velocity motor vehicle trauma. It is common to see associated fractures of the femur, acetabulum, or tibial plateau with this dashboard mechanism of injury.
In the classic study by Kennedy on complete knee dislocations, anterior knee dislocation was produced by hyperextension. Using 10 cadaver knee specimens, the authors produced exaggerated hyperextension. In this study, the ACL was torn first, followed by rupture of the PCL and posterior capsule at 30 degrees of hyperextension, and finally by tearing of the popliteal artery at 50 degrees of hyperextension (29,30). Hyperextension (with or without abduction or adduction forces) produces an initial tear of the ACL. As will be seen below, the clinical findings of hyperextension imply an injury involving the ACL before tearing of the PCL. Lastly, with rupture of both cruciate ligaments, tibiofemoral displacement occurs unchecked and the popliteal artery is at risk for injury (30).
Knee dislocations have been reported to have a high incidence of avulsion injury patterns of both ligamentous and tendinous insertions (31). Two early clinical reports documented a high incidence of cruciate ligament avulsions in knee dislocations. Sisto and Warren (32) and Frassica et al (33) in separate series noted similar percentages of PCL (88% and 77%, respectively) and ACL (63% and 46%, respectively) avulsions without relation to the velocity of injury (Table 51-1). Combining both series, PCL avulsions were noted in approximately 80% of knee dislocations and ACL avulsions were noted in approximately 50% of dislocated knees. This is in contrast to the high frequency

of midsubstance tears that are seen in isolated injuries to the ACL, as well as in contrast to our experience with high-energy knee dislocations. The majority of these high-energy knee dislocation injuries do not occur in association with a bony avulsion. Nonetheless, the possibility of cruciate ligament bony avulsion should be considered, as it can direct and simplify the treatment plan.
Table 51-1 Presence of Cruciate Ligament Avulsions in Knee Dislocations
  Avulsed Ligament
Author No. Knees Posterior Anterior
Sisto and Warren (32) 16 14 (88%) 10 (63%)
Frassica et al (33) 13 10 (77%) 6 (46%)
Total 29 24 (83%) 16 (55%)
(Reproduced with permission from Schenck RC Jr, Burke RL. The dislocated knee. Perspect Orthop Surg 1991;2:119–134.)
The effect of strain rate on the failure properties of the ACL was investigated by Noyes et al, who studied bone-ligament-bone preparations (34). The primary mode of failure was tibial avulsion at slow rates (0.67%/sec strain) and midsubstance failure at faster rates (67%/sec strain). In a similar strain rate study, Kennedy et al noted that the primary mode of failure of all ACL tears was midsubstance under both slow (40%/sec) and faster (140%/sec) strain rates. These laboratory strain rates, although termed slow and fast, are in reality both slow when viewed from a clinical perspective. In an attempt to create such strain rates in a cadaver cruciate ligament injury model in knee hyperextension, investigators noted that a variation in injury pattern of the PCL occurred with a change of strain or velocity (35). A high strain rate (∼l5,400%/sec) produced a stripping lesion of the femoral attachment of the PCL that correlated well with the “peel-off” lesion of the PCL seen clinically in hyperextension knee dislocation trauma. In the cadaver study the “stripping” or “peel-off” lesion occurred in an avulsion pattern but with small bony fragments, with the injury occurring through Sharpey’s fibers. With the low-velocity model (100%/sec strain), the PCL tore in a more consistent midsubstance pattern. The ACL was variable in its pattern of injury but tore in midsubstance with both high- and low-velocity injury rates. In this study the difference in ligaments was thought to be in part created by the femoral notch. The ACL is classically torn by the notch transverse to its fibers, whereas the PCL is torn with forces in parallel to the ligament, hence theoretically making the PCL more sensitive to strain rate than the ACL (Fig. 51-5) (36).
Signs and Symptoms
The physical findings associated with knee dislocations vary widely, ranging from an irreducible knee dislocation to a spontaneously reduced dislocation with only an effusion. Patients with a dislocated knee are easily recognized as a result of the obvious deformity. They cannot ambulate, they have severe pain, and they may demonstrate signs of neurologic and vascular injury. It is important to evaluate these patients regarding

the function of their extensor mechanism and to look for any open wounds and to carefully evaluate the neurovascular status (see below).
FIGURE 51-5 The strain-rate sensitivity of PCL rupture may be in part related to the direction of forces from the notch in hyperextension. ACL tearing occurs with forces crossing the ligament, whereas PCL tearing forces occur along the ligament, in effect making the PCL more strain-rate sensitive. (Redrawn after Schenck RC, Kovach IS, Agarwal A, et al. Cruciate injury patterns in knee hyperextension: a cadaveric model. Arthroscopy 1999;15[5]:489–495, with permission.)
Patients who sustain a knee dislocation that spontaneously reduces may have a relatively normal-appearing knee. Subtle signs of injury such as mild abrasions, a minimal effusion, or complaints of pain may be the only obvious abnormalities. An examination of the patient’s knee will generally reveal gross and obvious instability.
Patients with a knee dislocation combined with an ipsilateral lower extremity fracture are the most difficult diagnostic challenge. Frequently, orthopaedic surgeons concentrate on the obvious skeletal injuries and overlook the subtle signs of a spontaneously reduced knee dislocation. EUA following stabilization of the lower extremity fractures will reveal gross knee instability. It is important to examine the knee carefully following ipsilateral lower extremity or pelvic trauma. Data we have collected have demonstrated that 26% of our patients with tibial plateau fractures sustained as a result of high-energy trauma had an associated bicruciate ligament injury (37). Improved vigilance in this area by orthopaedic surgeons may partially explain the increased recognition of knee dislocations at many trauma centers.
Associated Injuries
The anatomy of the popliteal neurovascular structures explains their susceptibility to injury. The popliteal artery courses from the fibrous tunnel of the adductor hiatus through the popliteal space (giving off its five geniculates) and exits through the fibrous arch of the soleus muscle. Being securely fixed proximally at the adductor hiatus and distally at the soleus arch, the popliteal artery and vein can be torn or stretched with the exaggerated tibiofemoral displacement or hyperextension resulting in the dislocation (39).
Numerous reports have documented the incidence of vascular injuries in association with knee dislocations, ranging from 7% to 64% (19,21,29,36,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54). The wide range is a result of differences in study methodology, the methods of detection of knee dislocations, and the definition of a significant arterial injury. The mechanism of arterial injury varies with the type of dislocation. When anterior dislocations injure the artery, it is usually by traction, resulting in an intimal tear. In contrast, vascular injuries associated with posterior dislocations are frequently complete arterial tears (39). Green and Allen reported a higher incidence of vascular injury with posterior dislocations than with anterior dislocations (44% versus 39%, respectively) (39). Others have noted a higher incidence of vascular injury with anterior dislocations (52). Shelbourne et al (55) noted a lower incidence of vascular injuries with low-velocity knee dislocations (approximately 8%). In the series by Eastlack et al (22), the incidence of arterial injury was 12% in 28 consecutive knee dislocations seen at one large institution. Similarly, in the recently published series by Stannard et al, the incidence of arterial injuries in 134 knee dislocations was only 7% (47). As the diagnosis of knee dislocation is becoming more common as a result of the factors discussed earlier in this chapter, the incidence of significant arterial injury appears to be decreasing from earlier reports. Regardless of the exact percentage, the risk of arterial injury should always be considered, even in low-velocity knee dislocations.
It is the orthopaedic surgeon, as the primary treating physician for such injuries, who must initially evaluate the vascularity of the extremity. The difficulty in ensuring vascular integrity clinically has been well documented in many reports of knee dislocations (19,39,40,41,56,57,58,59,60). Furthermore, there is controversy concerning the use of arteriography in knee dislocations. Noninvasive arterial studies, including ankle–arm arterial pressure indices as well as the assessment of waveforms on the Doppler evaluation of arterial flow, are being more widely used in place of arteriography.
Misdiagnosis of vascular injury and delay in arterial repair based on adequate capillary refill and/or palpable peripheral pulses have been reported in the older orthopaedic literature (39). Some authors have noted that the presence of pedal pulses does not completely rule out an arterial injury. In a study by Jones et al, significant arterial injuries secondary to knee dislocations were discovered on arteriography in 4 of 15 (27%) limbs despite the presence of postreduction pulses that were judged to be normal. These authors advocated the liberal use of arteriography in knee dislocations (41). Because of this and other reports, arteriography, even in the presence of palpable postreduction pulses, has been advocated by some following knee dislocations (39,41). Obviously, the clinical examination must look for any evidence of ischemia, diminished flow, or a compartment syndrome. The presence of ischemia requires immediate surgical treatment. However, several authors have questioned the routine use of arteriography in all patients with knee dislocations. Stannard et al recently published a large series of knee dislocations using physical examination as the primary screening tool for significant vascular injuries. They reported on 126 patients with 134 knee dislocations who were evaluated using a protocol of “selective arteriography.” All patients were evaluated with serial physical examinations at the time of admission, approximately 4 to 6 hours later, and again at 24 and 48 hours. Any patient with an abnormal physical examination was then evaluated with arteriography. They found that the positive predictive value of physical examination was 90%, with one patient having a false-positive examination. More importantly, the negative predictive value was 100%, with no missed significant arterial injuries. The sensitivity of physical examination was 100%, while the specificity in their series was 99% (47).
Looking at the literature on vascular evaluation, six retrospective and two prospective studies using selective arteriography based on physical examination have been published. These eight studies have evaluated a total of 449 knee dislocations, with 85 (19%) having abnormal physical examinations and, of those, 59 (69%) having significant arterial injuries. Three hundred sixty-four patients had normal physical examinations, and not a single one of those patients had an arterial injury requiring treatment (47,48,49,50,61,62,63,64). Table 51-2 summarizes the findings of these eight studies published since 1992. The selective use of arteriography based on the findings of clinical examination with or without noninvasive vascular studies has

become the accepted standard of care based on these publications. One critical aspect of any vascular evaluation is having a specific protocol that is used institution-wide.
Table 51-2 Published Cases Using Physical Examination to Determine Need for Arteriography
Physician (year) Retrospective Studies
No. Knee Dislocations Patients with Abnormal Vascular Exam Patients with Arterial Injury Requiring Surgery Patients with Normal Vascular Exam Patients with Arterial Injury Requiring Surgery
Abou-Sayed (2002) 53 17 (32%) 8 (47%) 36 (68%) 0
Martinez (2001) 21 9 (43%) 2 (22%) 12 (57%) 0
Dennis (1993) 38 2 (13%) 2 (100%) 36 (87%) 0
Kendall (1993) 37 6 (16%) 6 (100%) 31 (84%) 0
Kaufman(1992) 19 4 (21%) 4 (100%) 15 (79%) 0
Treiman (1992) 115 29 (25%) 22 (75%) 86 (75%) 0
Miranda (2002) 32 8 (25%) 6 (75%) 24 (75%) 0
Stannard (2006) 134 10 (7%) 9 (90%) 124 (93%) 0
TOTAL (2006) 449 85 (19%) 59 (69%) 364 (81%) 0
With respect to an established popliteal artery injury and resultant ischemia, blood flow must be reestablished within 6 to 8 hours. Inadequacy of the collateral vessels in providing distal flow for limb survival was demonstrated clinically by the trauma experience in World War II. In the series by DeBakey and Simeone, 80% of soldiers suffering a popliteal arterial injury without revascularization eventually required an amputation due to inadequate collateral circulation (65). Furthermore, the time to revascularization is critical, and the series by Green and Allen in 1977 showed the critical time to be within 6 to 8 hours after injury (39). These authors observed that patients with popliteal artery injuries whose limb was not revascularized in this time period required an amputation 9 out of 10 times.
Using the information reported by Green and Allen, Jones et al, Stannard et al, Wascher, Schenck et al, and other publications over the past decade, a useful protocol for vascular management in knee dislocations can be derived (39,45,47,48,49,50,61,62,63,64,66):
  • The arterial flow of the posterior tibialis and dorsalis pedis pulses should be carefully evaluated in any patient with a knee dislocation.
  • Once the dislocation is reduced, the arterial flow should be reevaluated.
  • Clinical examination and noninvasive studies can be used to assess arterial flow. We recommend serial examinations for a period of up to 48 hours to allow the diagnosis of vascular occlusion resulting from increasing swelling, hematoma, or compartment syndrome. Any evidence of abnormal vascular flow requires immediate treatment.
  • If the arterial flow is not normal after joint reduction, the popliteal artery should be explored immediately. This may include on-the-table arteriography immediately prior to surgical exploration.
  • If arteriography is performed in the presence of abnormal circulation, surgical reanastomosis should not be delayed to obtain the study. Revascularization should be done an absolute maximum of 8 hours after injury whenever feasible.
  • It is unacceptable to suggest spasm as a cause for decreased or absent pulses in an attempt to justify observation. If arterial insufficiency is present, then it must be assumed that there is a vascular injury.
  • Arterial injury is treated with excision of the damaged segment and reanastomosis with a reverse saphenous vein graft, or occasionally by direct repair.
Neurologic Injury
The peroneal nerve is the nerve at greatest risk for injury in a knee dislocation. The incidence of injury has been reported to range from 14% to 35% (56,67). Although frequently discussed as occurring with a posterolateral dislocation,

the peroneal nerve is probably most commonly injured in association with the lateral ligamentous complex, as would result with a hyperextension-adduction injury to the knee. The peroneal and tibial nerves are not as firmly fixed as is the popliteal artery and are therefore less prone to injury. Nonetheless, nerve injury is usually a traction injury and frequently is not amenable to surgical repair (32,56). Stocking-type paresthesias should alert the clinician to the possibility of a compartment syndrome in the differential diagnosis. The paresthesias may not be due to neuropraxia of both tibial and common peroneal nerves. Complete nerve injuries are associated with a poor prognosis, with less than 50% regaining full functional recovery with nonoperative treatment (68,69,70). Currently, the exact indications for neurolysis or cable grafting are controversial. Patients with a peroneal nerve injury who are undergoing surgical repair or reconstruction of the posterolateral corner should probably be treated with at least a peroneal neurolysis (68,69). Tibial nerve injuries are less common than peroneal nerve injuries but carry an even graver prognosis for recovery of function (21,68).
Treatment Rationale
The literature is replete with small clinical series of knee dislocations, with most authors advocating early operative repair of the torn structures (3,19,29,32,33,45,49,55,58,67). Most series that advocate nonoperative treatment were published 15 or more years ago (44,46,71). While isolated reports of good function and stability with nonoperative management have been published, most authors have noted unacceptable rates of stiffness, pain, or instability (26,27,31,52,58,72,73,74,75). In 1972, Taylor et al reported on their experience with knee dislocations (46). They stressed the importance of the duration of immobilization, with generally good results obtained in 26 knees, and recommended immobilization of the knee in slight flexion for a period of approximately 6 weeks. The results from this study are instructive in understanding the balance between knee stiffness and instability in the treatment of the dislocated knee. The authors found that greater periods of immobilization produced a very stable but unacceptably stiff knee; in contrast, shorter periods of immobilization (less than 6 weeks) produced a knee with full range of motion but with unacceptable laxity and instability.
Surgical decision making can be enhanced by the use of MRI. Several investigators have used MRI to identify cruciate avulsions as well as to predict meniscal and chondral damage in knee dislocations (76,77). MRI has been used to distinguish avulsion or midsubstance injuries of the PCL prior to surgery. A finding of a midsubstance tear should alert the clinician to the more likely need for reconstruction. Discussion with the radiologist prior to the study helps to ensure that an adequate MRI evaluation of the intercondylar notch and its contents is obtained. MRI is also invaluable in patients with fracturedislocations, where the skeletal instability from the fracture makes obtaining an accurate ligament evaluation on physical examination virtually impossible. To obtain the best images and avoid artifact, the MRI should be obtained prior to skeletal stabilization with metallic implants.
Stress x-rays under anesthesia in varus and valgus with the knee in extension can be important for documentation of collateral ligament integrity or disruption. The combination of EUA, stress x-rays, and preoperative MRI allows an accurate preincision prediction of the torn ligaments (both location and type) in a patient with a knee dislocation (Fig. 51-6). This allows the surgeon to make sure that a graft for a PCL reconstruction is available if a midsubstance tear is present and to clarify the optimal placement of incisions for reconstructive ligament surgery. This approach has been used by several authors (78,79,80,81,82,83), with all noting a spectrum of soft tissue injuries on MR evaluation. Although MR information is extremely useful in the management of knee dislocations, the radiographic study is best used in conjunction with EUA.
FIGURE 51-6 Magnetic resonance images of a dislocated knee with complete tears of the MCL, PCL, and ACL with a “peel-off” lesion of the PCL (A) and a tibial avulsion of the MCL on coronal T1-weighted MRI (B).

In 1991, Shelbourne et al reported their experience with 21 patients with low-energy knee dislocations. They noted a low incidence of arterial injury (4.8%, 1 of 21 patients) with four patients (19%) suffering a peroneal nerve palsy. Knee stiffness was noted in patients who underwent simultaneous ACL/PCL reconstructions. They advocated mid-third patellar tendon reconstruction of the PCL as the initial ligamentous treatment in the knee dislocation (55). Furthermore, they described a staged approach to the treatment of the bicruciate injury, initially treating the PCL injury followed by range-of-motion exercises. Once motion was reestablished, an ACL reconstruction was performed. The success of this treatment plan has been verified by other investigators (79).
Although most reports emphasize the importance of early operative repair and the poor results obtained with closed treatment, no prospective trials to date have compared closed versus open treatment options with similar types of knee dislocations. With the recent advances in ligament reconstruction and repair techniques, it makes intuitive sense to perform acute ligamentous repairs. Harner et al recently published a series of knee dislocations that documented significantly better results with acute repair or reconstruction versus chronic reconstruction (84). Shields et al noted in 1969 that multiple structures are found within the joint and “it has been impossible for us to always tell before surgery the exact magnitude of the internal derangement. Thus to predict satisfactory outcome with conservative treatment is difficult, if not altogether impossible” (45). Despite this and numerous other arguments supporting acute ligamentous repair, a prospective study is needed to give further credence to the currently accepted operative treatment rationale (85).
Despite the concern of stretching a PCL graft or reattachment, aggressive, early range of motion is required in any postoperative knee dislocation rehabilitation protocol. Immobilization after operative reconstruction can result in permanent flexion loss and fixed flexion contractures. Furthermore, once stiffness occurs in such a clinical scenario, it is very difficult to correct even with current aggressive arthroscopic release, epidural pain management, and prolonged rehabilitation. With reattachment or reconstruction of the PCL, early motion should be started, with weight-bearing and functional rehabilitation added based on surgeon experience and preference. If 90 degrees of flexion has not been obtained by 4 to 6 weeks after bicruciate surgery, manipulation under anesthesia and arthroscopic scar excision is usually necessary.
While early and aggressive reconstruction is clearly becoming the preferred treatment option in most patients with knee dislocations, some patients may benefit from a less aggressive surgical approach. Examples include patients who have sustained severe closed head injuries, are morbidly obese, have open dislocations with a badly damaged soft tissue envelope, have an associated arterial or extensor mechanics injury, or are poor rehabilitation candidates. Closed reduction of the knee dislocation with a spanning external fixator for a period of 7 to 8 weeks, followed by removal of the external fixator and manipulation under anesthesia, may be the only available treatment option for these patients (Fig. 51-7) (26,27,74,75). Care must be taken to place the pins far enough away from the joint so that future ligament reconstruction is not compromised by the pin tracks. It is critical to obtain an x-ray or fluoroscopic evaluation of the quality of the reduction after placing the external fixator but before leaving the operating

room. Leaving a patient with a spanning external fixator and a subluxed knee will usually result in a very poor outcome. Physical therapy should be prescribed following removal of the external fixator for a period of 6 to 12 weeks, followed by an assessment of the patient’s motion, pain, and stability. If the patient has achieved acceptable motion and the knee is unstable, a delayed reconstruction of the ligament injuries is appropriate. Again, overall patient recovery from a closed head injury or lifethreatening trauma will dictate the appropriateness of surgical reconstruction.
FIGURE 51-7 A. Reduced knee joints using external fixation after bilateral knee dislocations with bilateral popliteal artery tears. B. Removal of external fixation at 6 weeks, manipulation under anesthesia, and ligament evaluation. (B, Copyright Schenck RC, Jr. Albuquerque, NM. Reprinted with permission)
The decision regarding which multi-trauma patients should be treated with early repair or reconstruction and which should be treated with a spanning external fixator must be individualized. It is certainly possible to get a good result with early reconstruction in a patient with a head injury, and that may be the appropriate treatment course if the patient is young and is thought to have good potential for recovery from the head injury.
Diagnosis and Classification
Several authors have questioned the long-held opinion that both cruciate ligaments must be torn for a knee dislocation to occur. As early as 1975, Meyers et al referred to the knee dislocation with an intact PCL (58). Shelbourne et al and Cooper et al have recently reported on patients with a radiographically defined knee dislocation that, upon reduction or operative exploration, demonstrated a functioning PCL (86,87,88,89,90). Interestingly, many of these patients were noted to have a partial PCL tear. Similarly, an ACL intact knee dislocation has been noted to occur with posterior position of the tibia on the femur with complete tearing of the PCL (Fig. 51-8). It is now a well-accepted phenomenon that the knee can dislocate with an intact ACL or an intact PCL. A PCL-intact knee dislocation is usually an anterior knee dislocation with either involvement of the MCL or LCL (Fig. 51-9).
A PCL-intact knee dislocation differs greatly from a classic knee dislocation, a complete bicruciate injury. Although the decision must be made between immediate versus delayed ACL reconstruction, the presence of a functioning PCL changes surgical management to the more simple treatment of the ACL and associated corner injuries. Furthermore, a functioning PCL in theory would appear to protect the popliteal artery, as tibiofemoral distraction is limited (86): that is, the dislocated knee with an intact PCL probably has a decreased risk of arterial injury compared to a classic knee dislocation. This final point of vascular risk is only theoretical, as there are limited reports of the PCL-intact knee dislocation. Nonetheless, the PCL-intact knee dislocation should be considered a distinct entity from one where complete tears of both cruciate ligaments occur. Thus, the description of a knee injury as a dislocation does not clearly define either the injury or the treatment (57,91,92). Classification of such an injury must include specifically what is torn.
Fracture-dislocation of the knee as described by Moore in 1981 involves a ligamentous injury in association with a fracture of the tibial or femoral condyles (93,94). This entity should be distinguished from the purely ligamentous definition and is discussed later in this chapter. Avulsion injuries such as the Segond fracture, fibular head avulsion fractures, and cruciate avulsions may occur in knee dislocations, but they should be considered ligamentous injuries and not condylar injuries that destabilize the bony architecture of the knee. Nonetheless, the understanding of this concept of fracture-dislocation is useful in treating the spectrum of injuries involving the knee and will be described in detail below.
FIGURE 51-8 A. ACL-intact knee dislocation with a posterior tibiofemoral position. B. Reduction MRI revealing the intact ACL.
FIGURE 51-9 Lateral x-rays comparing a PCL-intact knee dislocation (A) and a complete bicruciate ligament knee dislocation (B) in two different patients. Note the parallel alignment of the patella with the femur in the complete bicruciate injury and (B) the close proximity of the femur and tibia in the PCL-intact knee dislocation (A).

In 1963, Kennedy classified knee dislocations in terms of tibial position with respect to the femur (ie, an anterior knee dislocation implies that the tibia is dislocated straight anterior to the femur) (29). He noted five main types of dislocation: anterior, posterior, lateral, medial, and rotatory (Fig. 51-10). Rotatory dislocations are classified into four groups (anteromedial, anterolateral, posteromedial, and posterolateral), with posterolateral being the most frequently described type of rotatory knee dislocation (37,53,66). This classification system has been frequently cited in the literature (19,32,33,39,41,44,45,46,55,58,67).
FIGURE 51-10 Classification of knee dislocations based on displacement of the tibia on the femur. (Reproduced with permission of Schenck RC. The dislocated knee. AAOS Instructional Course Lectures 1994;43:127–136.)
Although the least common of knee dislocation types, the posterolateral dislocation is well described. The hallmark of this condition is its irreducibility, as it is a true complex dislocation where the medial femoral condyle buttonholes through the medial capsule and the medial collateral ligament invaginates into the knee joint, preventing closed reduction (56,67). A transverse furrow, seen on the medial aspect of the knee, is the sine qua non of this knee dislocation type. The mechanism of injury as described by Quinlan and Sharrard is that of an abduction force applied to the flexed knee, coupled with internal rotation of the tibia (67). Peroneal nerve palsy is frequently associated with this type of dislocation, resulting from a traction injury to the nerve over the lateral femoral condyle. Skin necrosis secondary to pressure from the medially displaced femur has been reported (Fig. 51-11) (56).
The position classification system of knee dislocations is well established and very useful in alerting the physician to the mechanism of injury, the reduction maneuver needed, and in some situations potential associated injuries (Table 51-3). Nonetheless, the system has significant limitations. In various series of knee dislocations, as many as 50% had spontaneously reduced at the time of medical evaluation; hence, they were unclassifiable by the position system. Secondly, position classification only suggests possible ligamentous involvement. With the possibility of a PCL-intact knee dislocation, tearing of both cruciate ligaments is not guaranteed in a knee dislocation. Furthermore,

the exact status of the collateral ligaments and corners is also not defined with a straight anterior or posterior knee dislocation. The knee ligament anatomy is complex, with many combinations of cruciate and collateral disruptions possible with a knee dislocation. Thus, it is useful to classify knee dislocations in terms of the ligaments involved, and this is best performed soon after the injury (if tolerated) as well as during EUA. One should be able to identify one of at least five possible injury patterns based upon an anatomic classification (Table 51-4).
FIGURE 51-11 Posterolateral dislocation of the knee presenting 3 weeks postinjury with grossly positive tibial dropback and medial furrowing with early soft tissue necrosis (A). Magnetic resonance view of the same knee in the dislocated position (B).
This classification, termed the anatomic system, is based upon ligament function (ie, what is torn) and is very useful in deciding upon treatment options and surgical approach. The higher the number, the greater the injury to the knee, and in most scenarios, the greater the velocity of injury. Additional letters of C and N are used to designate associated injuries: C indicates an arterial injury and N indicates a neural injury, be it the tibial or more commonly the peroneal nerve. Thus, a KDIIILCN implies a complete bicruciate injury with the LCL and posterolateral corner torn, with an injury of the popliteal artery and a nerve injury (most commonly the peroneal nerve). Further subsets can identify injuries to the menisci or injuries to tendons (ie, patellar tendon rupture or iliotibial avulsion).
Table 51-3 Position Classification of Knee Dislocations
ANTERIOR Most common type
Frequent arterial injury (traction)
Hyperextension most common mechanism of injury
POSTERIOR Frequent arterial injury (complete tears)
High association with extensor mechanism disruption
Medial femoral condyle buttonholed through medial capsule
High incidence of peroneal nerve palsy
Transverse skin furrow medially
In one series of 13 dislocations by Walker et al and further follow-up of 28 dislocations by Eastlack et al, the anatomic system was used to classify injuries and direct treatment (22,95,96). In those series, KDIIIL injuries fared worse than KDIIIM dislocations, with a greater incidence of postoperative arthrofibrosis, longer disability, greater laxity on KT-1000 testing,

poorer scores on outcome measures, and poorer scores on the modified Lysholm and International Knee Documentation Committee (IKDC) scales. The KDIII was the most common type of knee dislocation seen. KDIV (all four ligaments torn) was rarer and usually involved high-energy motor vehicle trauma. The anatomic system is useful as it requires the clinician to focus on what is torn, thereby directing treatment to what is torn, and especially directing treatment toward the corner and collateral ligament involved. It also allows for accurate discussion of injuries between clinicians and allows for comparisons of like injuries in this wide spectrum of knee dislocations.
Table 51-4 Anatomic Classification of Knee Dislocation
Classification Injury Pattern
KDI Single cruciate torn and knee dislocated: usually ACL/collateral ligament torn, PCL intact (PCL intact knee dislocation), or PCL/collateral ligaments torn, ACL intact
KDII ACL/PCL torn, collateral ligaments intact (experimentally produced by Kennedy but clinically rare)
KDIIIM ACL/PCL/MCL torn, LCL, posterolateral corner (PLC) intact;
KDV Knee fracture-dislocation (Fx-Dx)
KDV.1 Fx-Dx ACL or PCL intact
KDV.2 Fx-Dx with a bicruciate injury
KDV.3 Fx-Dx, bicruciate injury, one corner
KDV.4 Fx-Dx, all four ligaments injured
The KDV classification indicates a knee dislocation combined with a periarticular fracture. The KDV classification is further stratified to describe the ligamentous injury associated with the fracture. KDV.1 is a fracture dislocation with either the ACL or PCL intact. KDV.2 is a bicruciate injury. KDV.3 is a bicruciate injury plus injury to one corner, in addition to the fracture. KDV.4 is a fracture-dislocation associated with tears of all four ligamentous regions of the knee. This modification clearly documents the extent of ligament damage in patients with fracture-dislocations (47).
Surgical and Applied Anatomy
Knee injuries are frequently, and appropriately, viewed from the vantage point of isolating the injury to the correct diagnosis, with usually one or two structures torn. In the arena of the knee dislocation, in contrast, multiple structures can be injured, with definite patterns of injury described. As noted earlier in this chapter, the classification of knee dislocations is most accurately determined by the ligaments torn (the anatomic system); hence, knowledge of the structure and function of the knee ligaments is very important in classifying and defining the injury pattern. Furthermore, the association of disruption of musculotendinous structures (patellar tendon, patellofemoral dislocation, iliotibial band, biceps femoris, gastrocnemius, and popliteus) and the importance of associated injuries adds to the variability of the anatomy involved in knee dislocations. Lastly, the bony architecture is important, as joint surface fractures can occur with a knee dislocation and are frequently underreported. Depending upon the size of fracture fragments, the knee injury can be classified as a fracture-dislocation when associated with a large condyle fracture rather than a pure ligamentous injury as implied with the term “knee dislocation.”
Conceptually, defining the knee as a joint composed of four major ligamentous structures (ACL, PCL, posteromedial corner/MCL, and posterolateral corner) is very useful. The ACL and PCL can be torn in tandem (bicruciate injury), separately (ACL or PCL intact knee dislocations), or rarely not torn at all (a cruciate-intact knee dislocation) (Fig. 51-12). The injuries to the collaterals are frequently complete, with involvement of at least one of the ligamentous corners. The anatomic arrangement of the popliteus, the popliteofibular ligament, and the biceps femoris posterolaterally and the semimembranosus/posterior oblique ligament complex posteromedially allows for injury of those structures in conjunction with the major ligament injury.
Anterior Approach
The anterior approach to the knee allows for exploration of the knee joint, synovectomy, fracture fixation, and repair of

the extensor mechanism. The patient is placed in a supine position and a small linen roll is placed under the ipsilateral buttock. A tourniquet is applied to the proximal thigh. A straight incision beginning proximal to the superior pole of the patella is carried distally, directly over the patellar tendon and medial to the tibial tubercle. The length of incision depends on the pathology being treated. Exposure of the extensor mechanism involves incision of the arciform layer, the condensation of layer I anteriorly, just deep to the subcutaneous fat. Subcutaneous dissection should not be made superficial to this fascial layer as devitalization of the overlying skin can occur, especially if a concurrent lateral retinacular release is performed. If joint exposure is required, the quadriceps tendon is incised in its midportion, followed by a medial capsulotomy carried distally and medially to the tibial tubercle. A cuff of capsule at least 5 mm wide should be preserved on the medial edge of the patella for closure. Inadequate longitudinal release of the quadriceps tendon can result in avulsion of the tendon from the tibial tuberosity when the patella is displaced laterally. This incision allows exposure of the anterior knee, distal femur, and proximal tibia. The tibial tubercle and patellar tendon limit exposure of the lateral knee joint. Frequently, when open exposure of the notch is needed for cruciate reattachment, an incision from the medial edge of the pole of the patella can be carried down medially to the anterior tibial plateau to achieve adequate exposure. Viewing the contents deep within the notch frequently requires use of a headlamp in such open approaches (18).
FIGURE 51-12 Knee dislocations present with varying ligament injury patterns. A. X-ray of a knee in an adolescent with a cruciate ligament-intact rotatory dislocation of the tibiofemoral joint (note the anteroposterior view of the femur and lateral view of the tibia). B,C. Reduction anteroposterior and lateral x-rays of the injured knee. EUA and MRI revealed integrity of both the cruciate and collateral ligaments.
Lateral Approach
The lateral approach is useful for open reduction and internal fixation of distal femoral condyle fractures (femoral-sided fracture-dislocations of the knee), tibial plateau fractures, and reattachment of knee ligaments and lateral tendons. The patient is positioned supine with a small bolster under the ipsilateral hip. The incision is placed over the lateral side of the lateral femoral condyle, anterior to the iliotibial band, and is carried distally over Gerdy’s tubercle. The fascia lata is opened parallel to the skin incision, anterior to the iliotibial band. If proximal extension is necessary, the vastus lateralis is elevated off the lateral intermuscular septum and perforating vessels are ligated. Retractors are placed subperiosteally over the anterior aspect of the femur, exposing the entire distal aspect of the lateral femur. The patellofemoral joint can be exposed by incising the lateral transverse patellar ligament. Splitting the vastus lateralis muscle through its belly should be avoided as it can cause excessive bleeding with loss of control of the perforating vessels. Posterior exposure with this approach is limited by the fibular collateral ligament and common peroneal nerve (18).
Posteromedial Approach
The posteromedial approach is very useful for access to the vascular structures of the popliteal fossa, and it is the utilitarian approach to these vessels. Variations of this approach have been used by Burks et al (Fig. 51-13) (36) and Berg (97) to approach the tibial attachment of the PCL when using the inlay PCL reconstruction technique (Fig. 51-14) (97). Additionally, the cruciates

and the posteromedial corner can be accessed via this approach. It has also been described by Muscat et al (98) for simultaneous repair of vascular injuries and ligaments when associated with a traumatic knee dislocation (Fig. 51-15). The approaches to the PCL described separately by Burks et al and Berg involve a posterior incision into the flexion crease of the knee combined with a similar deep-plane dissection as described below.
FIGURE 51-13 The posteromedial approach to the tibial attachment of the PCL using an incision in the knee flexion crease and partial detachment/release of the gastrocnemius tendon as described by Burks.
FIGURE 51-14 PCL reconstruction as described by Berg. A. Lateral decubitus position, and arthroscopic preparation of the PCL femoral origin. B. Posterior approach to the tibial insertion for the inlay technique. C. Deep dissection of the posterior knee with detachment of the medial head of the gastrocnemius. D. Final reconstruction with a tibial inlay, arthroscopic femoral PCL reconstruction technique. (Redrawn after Berg EE. Posterior cruciate ligament tibial inlay reconstruction. Arthroscopy 1995;11:70–73, with permission.)
The posteromedial approach can be easily accomplished in the supine position with the knee flexed and the hip externally rotated in the figure-four position. Preferentially the incision is placed over the medial epicondyle and extends distally. The incision is placed along the posterior aspect of the medial femoral epicondyle and courses distally along the posterior edge of the proximal medial tibia. The saphenous vein is identified and should be protected if possible. The saphenous nerve should be retracted posteriorly with the skin flap and the saphenous vein to avoid neuroma formation. For vascular access, the tendons

of the pes anserinus are usually transected 2 cm proximal to their tibial insertion. The proximal portion of the pes is reflected with the posterior flap, and the distal portion of the pes is reflected anteriorly. This allows exposure to the medial gastrocnemius. When using this approach just to repair the PCL, the medial meniscus, or the MCL/POL complex, the pes is mobilized but left intact. The medial gastrocnemius head may be detached (partially or completely) from the medial femur to allow exposure of the popliteal artery from Hunter’s canal to its trifurcation. With an approach to the PCL or the medial knee ligaments, the medial gastrocnemius tendon should be left intact. Exposure requires development of the plane between the posteromedial knee joint capsule anteriorly and the medial gastrocnemius posteriorly. All retractors must remain anterior to the medial gastrocnemius to protect the popliteal vessels. This approach is complex, and ideally it should be performed on a cadaver specimen or with an experienced surgeon to clearly understand it. It is easy to inadvertently dissect posterior to the medial gastrocnemius belly or anteriorly into the joint capsule. Keeping the knee flexed to 70 degrees relaxes the posterior muscles, simplifying the identification of the plane anterior to the gastrocnemius. Damage to the saphenous nerve can produce persistent medial knee pain from a traumatic neuroma. Furthermore, the incision should be placed posteriorly over the muscle bellies in the leg, since incisions directly over the tibia can result in skin necrosis. In the presence of a knee dislocation and evidence of MCL insufficiency, capsular structures are usually completely disrupted, allowing exposure of the knee joint itself. Access to the lateral side of the knee is limited with this approach (Fig. 51-16).
Posterolateral Approach
This approach is useful for reconstruction of the posterolateral corner, mobilization of the lateral gastrocnemius muscle for use as a muscle pedicle flap, and exploration and repair of the common peroneal nerve. It is frequently useful in knee dislocations for reattachment or repair of the cruciate ligaments and the posterolateral corner. The peroneal nerve is always isolated prior to deep joint exposure to prevent inadvertent injury to it. In dislocations with complete tears of both cruciates, the ligaments are frequently disrupted circumferentially in a half-circle starting at the patellar tendon anteriorly, with disruption of the lateral corner and the ACL, and with enough force to the PCL medially. With such injury, exposure of the tibiofemoral joint

can be facilitated by following the tissue planes created by the dislocation (15).
FIGURE 51-15 Posteromedial approach (from Schenck) to the tibial attachment of the PCL. The patient is placed in a supine position with the knee flexed 30 to 60 degrees and the leg and hip externally rotated. A. A skin incision is placed at the back edge of the medial tibia, coursing proximally to the posterior edge of the medial epicondyle. Superficial dissection is made through the sartorius fascia along the line of the skin incision. B. Deep dissection is made between the posterior knee joint capsule and the gastrocnemius. Partial detachment of the semimembranosus is required to access this interval. C. Exposure of the proximal tibia and capsulotomy allow identification of the PCL. Reattachment of avulsion fractures of the PCL and exposure for tibial inlay PCL reconstructions can be made through this approach, avoiding prone positioning of the patient. Externally rotating the tibia on the femur in conjunction with knee flexion allows access to the PCL. (Redrawn after Schenck RC. PCL surgery. AAOS videotape #10116,100, with permission.)
The patient is placed in the supine position with a tourniquet on the thigh and a small bump under the ipsilateral buttock. The knee joint is best exposed with it flexed to 90 degrees. This allows relaxation of the peroneal nerve and allows for better protection of the nerve throughout the procedure. The skin incision is placed in line with the fibular head and carried in a straight line proximally, then curving onto the lateral thigh. With proximal extension, the incision should curve between the iliotibial band and the biceps femoris tendon. The incision is carried down to the deep fascia, which is then opened carefully with scissors. At this point the nerve must be identified. It can usually be palpated subfascially as it courses from the biceps femoris through its perineural fat to the fibular neck. This approach should always include exposure of the peroneal nerve prior to deep dissection. The peroneal nerve is best isolated proximally and dissected distally where it wraps around the fibular neck. Once identified, the nerve is protected with a small vessel loop. The nerve can suffer injury with simple exposure, and the patient should be counseled in this regard preoperatively. Once the nerve is identified and protected, exposure of the posterolateral structures is carried out by making two additional fascial incisions. The first develops the interval between the biceps femoris tendon and the iliotibial band, giving access to the distal attachments of the LCL, the popliteofibular ligament and the popliteus tendon. The lateral gastrocnemius is mobilized posteriorly, exposing the posterolateral capsule. The second fascial incision splits the iliotibial tract over the lateral epicondyle. This provides access to the proximal attachments of the LCL and popliteofibular ligament as well as the femoral attachments of the posterolateral capsule. In the exposure of combined ligament injuries of the posterolateral knee, the dissection planes (and peroneal nerve) are usually already formed secondary to the displacement occurring with the knee injury. Straying posterior to the lateral gastrocnemius places the popliteal neurovascular structures at risk. This approach provides minimal access to the medial side of the knee. If the posterolateral corner and LCL are intact, the PCL cannot be exposed from this approach. Furthermore, if the approach is performed for a complete injury of the PCL and the posterolateral corner, an intact ACL will prevent access medially to the PCL insertion on the tibia. In such a scenario, a posteromedial incision will be necessary to access the PCL insertion site (Fig. 51-17) (15).
Posterior Approach
This approach provides access to the popliteal fossa, the posterior surface of the femoral condyles, the posterior knee capsule, and the posterior aspect of the distal tibia. It is useful for resection of tumors from the popliteal fossa or posterior knee, nerve or blood vessel exploration, and reattachment of PCL avulsions from the tibia.
The patient is placed in a prone position. A tourniquet is placed on the thigh. The skin incision begins posteromedially over the semitendinous and semimembranosus tendons, curves transversely across the knee flexion crease, and then proceeds laterally over the fibular head and fibula. The sural nerve and short saphenous vein are identified and the vein is followed proximally to the trunk of the popliteal vein. The short saphenous vein and sural nerve pierce the fascia of the posterior knee in the area of the distal flexion crease. The

medial and lateral gastrocnemius muscle heads are identified. The popliteal nerve, vein, and artery are exposed with ligation of the genicular branches as required. It is best to approach the vessels from the medial, proximal end of the fossa and work distally. The vessels and nerve may be retracted together, or alternatively the vessels may be retracted medially and the nerve laterally. Exposure of the femoral and tibial surfaces is performed through the neurovascular interval, with care taken to protect these structures. Distally, the popliteus muscle is found on the posterior aspect of the tibia and can be retracted to allow exposure of the proximal tibia (Fig. 51-18). Blunt dissection is safest for access to the proximal tibia. This is best performed with a finger or blunt scissors to avoid injury to the neurovascular bundle. Release of the medial gastrocnemius head can be performed to allow better exposure of the proximal tibia (15).
FIGURE 51-16 Sequential images of screw fixation of tibial avulsion of the PCL. A. Lateral femoral condyle fracture and bony avulsion of the PCL with an initial open reduction and internal fixation of the lateral femoral condyle. B,C. Then, through a posteromedial approach, open reduction and internal fixation of the PCL avulsion using a 4.0-mm cannulated A-O screw was achieved. D. Final radiograph.
The greatest danger is the potential for injury to the neurovascular structures of the popliteal fossa that are directly exposed in this approach. Because the patient is in a prone position, access to the anterior knee is difficult, making PCL reconstruction impossible without turning the patient supine during a portion of the procedure (requiring repeat prepping and draping). To approach the tibial attachment of the PCL, the posteromedial approach is preferred as it does not require a prone position (higher pulmonary and cardiovascular risk with a trauma patient), does not require direct exposure of the complicated anatomy of the popliteal neurovascular structures, and with the posteromedial approach described by Schenck allows access to the anterior knee.
Current Treatment Options
Treatment options for knee dislocations always begin with an evaluation for neurologic, vascular, and open soft tissue injuries. The vascular and open injuries must be addressed on an emergent basis and will determine the treatment course for the patient. Once these urgent issues have been addressed, the treatment

options can be divided into the categories listed in Table 51-5, where the advantages and disadvantages of each are listed.
FIGURE 51-17 Posterolateral approach to the knee. The skin incision is curved from the lower edge of the iliotibial band proximally to the fibular head distally. This approach requires release of the peroneal nerve.
There is not one single option that is the correct choice for all patients following a knee dislocation. Each of the current treatment options has advantages and disadvantages, which must be weighed against the unique injuries and situation of each patient. Surgeons who develop a practice with a high volume of knee dislocations should become familiar with all of the techniques listed and apply them based on the needs of their patients as well as their individual skills.
FIGURE 51-18 A. Exposure of the posterior aspect of the knee requires prone positioning and is made in an S-fashion crossing the flexion crease. B. Deep dissection is carried between the gastrocnemius heads and requires careful isolation and retraction of the popliteal neurovascular structures.
With respect to the reattachment of an avulsed PCL, Trickey and Torisu in separate reports showed good clinical results in reattaching an avulsed PCL (and bony fragment) with a screw (93,99,100,101,102,103). Reattachment of a cruciate or collateral avulsion is easily performed using screw or suture techniques. When a large bony fragment is present, screw techniques are useful. In hyperextension injuries, the PCL may be stripped from its femoral origin with small bony fragments but with limited midsubstance damage. This injury pattern has also been described as a “peel-off” lesion. Reattachment of the PCL with heavy nonabsorbable braided sutures (no. 5) using a Krackow suture technique has been described (Fig. 51-19) (104,105,106,107). Simultaneous repair of the associated posterolateral or posteromedial corner is performed. Our experience is that suture reattachment of the cruciate ligaments is usually inferior to that of reconstruction. Nonetheless, reconstruction is a more complex procedure than reattachment (108), requiring surgical experience with the procedure.
Recently, three separate investigators used initial early range of motion followed by simultaneous cruciate reconstructions performed arthroscopically. Fanelli et al reported their experience using early range of motion for the first 3 to 6 weeks after the injury in knee dislocations, followed by simultaneous cruciate reconstructions using allograft/autograft tissue for the PCL and ACL grafts (109). Delayed repair of the posterolateral corner was performed in some cases. They urged care in the technical placement of the tibial tunnels to maintain an adequate bony bridge. Wascher et al (20,75) used a similar technique of simultaneous cruciate reconstructions after achieving an initial

range of motion. Allograft tissues were used to reconstruct the cruciates. Simultaneous bicruciate reconstructions can simplify management by eliminating an additional reconstruction/rehabilitation period as required with staged procedures. In our experience, the risk of failure of a delayed repair of the posteromedial or posterolateral corner in such a scenario must be considered in such a treatment plan. Lastly, the technical requirements in tensioning the PCL graft first in the flexed knee (90 degrees) followed by tensioning the ACL (in extension) are essential to any bicruciate reconstruction technique.
Table 51-5 Current Treatment Options
Treatment Indications Advantages Disadvantages
Early Open Repair (First week) Avulsions with large bony fragments
  1. Secure fixation
  2. Maintain native ligaments
  1. Most injuries are either midsubstance tears or are avulsions without bone and repair is not possible
  2. Wound healing problems due to soft tissue envelope injury
  3. Increased risk of stiffness
Acute (2–4 weeks) reconstruction of all ligaments Knee dislocation with bicruciate injury and no large bony fragments
  1. Early restoration of ligament
  2. Fewer surgical procedures than staged cruciate reconstruction
  3. Allows early rehabilitation
Length of surgery
Acute (2–4 weeks) reconstruction cruciates staged with delayed (6 weeks) ACL reconstruction Knee dislocation with bicruciate injury and no large bony fragments
  1. Shorter initial procedure
  2. Return to OR at 6 weeks allows manipulation to increase motion
  3. Allows early rehabilitation
  1. Requires one additional surgery
  2. Rehabilitation in the first 6 weeks as in an ACL-deficient knee
Delayed (>1 month) reconstruction after motion is reestablished and ipsilateral injuries are healed Knee dislocation with soft tissue injury
  1. Establishes good motion prior to surgery
  2. Simultaneous bicruciate reconstruction better tolerated
  1. Delays full reconstruction
  2. Delays functional recovery to job, sports, etc.
  3. More difficult to obtain stable knee with chronic reconstruction
Early spanning external fixator with removal at 6–8 weeks, manipulation, and reconstruction if necessary after motion is obtained Knee dislocation in poor rehabilitation candidate
  1. Avoids lengthy procedure with significant complications until rehabilitation potential is clarified
  2. Fewer complications
  1. Difficult to obtain functional result equivalent to early reconstruction
  2. Delayed recovery
  3. Staged procedure that may require additional surgeries
  4. Risk of infection
A recent ly published preliminary report described the use of a hinged external fixator (Compass Knee Hinge, Smith & Nephew, Memphis) as an adjunct to ligamentous reconstruction following knee dislocations. The investigators reported favorable results combining the hinged fixator with an aggressive early motion rehabilitation program. The results showed excellent motion with improved stability compared to treatment with a conventional knee brace and early motion (Fig. 51-20) (47).
Outcomes can be difficult to assess in the literature because most series are small and a wide variety of treatment methods are reported. The combined results of several studies published since 1990 report that 38% of patients undergoing KD reconstructive surgery required an additional surgical intervention due to unacceptable postoperative knee motion (5,25,36,72,84,111,112,113,114,115). Similarly, the combined results of 16 studies published since 1990 yields a mean incidence of postoperative instability of one or more ligaments of 37%, with a range from 18% to 61% (22,61,68,97,116,117,118,119,120,121,122,123,124,125,126,127). Pain may be the most common adverse outcome following knee dislocation, with a reported incidence of 25% to 75% (22,61,97,116,120,124,125,128).
FIGURE 51-19 Sequential steps of placing Krakow locking loop ligament sutures for tendon or ligament repair. (Redrawn after Krackow KA, Thomas SC, Jones LC. A new stitch for ligament tendon fixation: brief note. J Bone Joint Surg [Am] 1980;68:359, with permission.)
FIGURE 51-20 A. Left knee dislocation (complete midsubstance bicruciate, KDIIIL) with multiple trauma, an avulsed fibular collateral ligament, and a disrupted extensor mechanism. B. The initial spanning external fixation was converted to a Compass Knee Hinge (Smith & Nephew Richards, Memphis, TN). It was applied as seen on the AP radiograph, after reattachment of the fibular collateral ligament and repair of the extensor mechanism. The cruciates were not reconstructed at this stage. C. Lateral x-ray of same articulating knee hinge. (Copyright Robert C. Schenck, Jr. Albuquerque, NM. Reprinted with permission)
FIGURE 51-21 A. AP intraoperative x-ray of pin placement prior to reaming the cruciate tunnels. B. The lateral x-ray with pins in the planned tunnels prior to reaming. The posterior pin does not penetrate the posterior capsule, and there is an adequate bony bridge between ACL and PCL tunnels in the proximal tibia.
FIGURE 51-22 A. The transtibial arthroscopic tunnel created for posterior cruciate ligament reconstruction has some theoretical disadvantages. B. Creating the tunnel properly necessitates a posterior and relatively distal position on the tibia to recreate the PCL insertion site. C. This lateral x-ray of a failed PCL reconstruction using a transtibial tunnel approach shows the tunnel was placed too anteriorly. (A, B, redrawn after, and C from Scott WN, Insall JN. Video textbook. Philadelphia: JB Lippincott, with permission.)
FIGURE 51-23 A. Two-tailed separate bundle reconstruction of the femoral side of the PCL combined with the tibial inlay technique distally. Lateral (B) and anteroposterior (C) x-rays showing proper placement of a tibial inlay graft and a standard femoral reconstruction of the anterolateral bundle of the PCL. Note the direction of the femoral interference screw placed endoscopically.
FIGURE 51-24 A. Posterolateral exposure of the knee with release of the peroneal nerve. B. Repair of the posterolateral ligamentous structures of the knee using Krackow suture construct.







Pearls and Pitfalls
Full recovery from a knee dislocation frequently takes 1 to 2 years. It is important to emphasize the time and energy commitment to the patient at the beginning of the process. Postoperative range of motion should be monitored carefully and the patient should be taken back to the operating room for a manipulation under anesthesia with or without an arthroscopic lysis of adhesions if the patient has not achieved at least 90 degrees of flexion by 2 months following reconstruction. Their ability to achieve full extension should be carefully monitored, and any flexion contracture should be aggressively treated with physical therapy hanging weights in extension. The patient should be told to avoid placing a pillow under the knee for comfort in the first 6 weeks following surgery, as this habit can lead to a flexion contracture.
As noted in the brief description of outcomes earlier in this chapter, problems with postoperative motion occur in more than one third of patients (110). Severe pain frequently accompanies the loss of motion. A motivated patient combined with a surgeon who is extremely vigilant regarding the risk of motion problems can decrease the incidence of motion loss requiring a return to the operating room to 10% or less. It is important to take the patient back to the operating room for a manipulation and/or arthroscopic lysis of adhesions early in the rehabilitation process if he or she is developing problems with arthrofibrosis (155).
Heterotopic Ossification
The occurrence of heterotopic ossification has been recently reported in the orthopaedic literature following knee dislocations. One study on 57 patients noted heterotopic ossification in 26% (155,156,157,158,159); only 12% of the patients, however, developed grade III or IV heterotopic ossification. The most common location of the heterotopic bone was medial, and it occurred both in patients with and without a medial surgical approach. The second most common location of the ectopic bone was posterior. There was a clear trend toward developing heterotopic ossification in patients following open dislocations and infections. It also occurred more frequently in patients who had had heterotopic ossification in other anatomic locations or had a prior history of it. Consideration should be given to prophylaxis against heterotopic ossification in patients who have a closed head injury, an open dislocation, develop an infection, or have a prior history.

Recurrent Laxity
As noted above, 37% of the patients reported to have knee dislocations in published outcome studies since 1990 have developed recurrent laxity of at least one ligament. This degree of instability may be lower in patients treated with contemporary surgical techniques, including the inlay PCL reconstruction, and simultaneous bicruciate reconstructions.
Controversies/Future Directions
Double-Bundle PCL Reconstructions
The concept of a double-bundle PCL reconstruction is an attempt to recreate the functional anatomy of the PCL. The larger bundle is the anterolateral bundle, which is tensioned with the knee in flexion. The smaller posteromedial bundle is tightened with the knee in relative extension (approximately 15 degrees of flexion). The combination of these two bundles may improve the stability of the PCL through the entire arc of motion. A recently published study of 30 PCL reconstructions combining the inlay technique and double-bundle technique reported excellent stability 2 to 3 years following reconstruction (123).
Inlay Versus Transtibial Tunnel PCL Reconstruction
Berg initially reported the concept of creating a trough on the back of the tibia and inlaying a graft at the anatomic insertion of the PCL, rather than drilling a transtibial tunnel. He described the problem of the graft having to traverse around the “killer turn” when the transtibial tunnel is employed, and that this might lead to graft failure (97,160). Markolf confirmed in a biomechanical study that traversing the “killer turn” caused one third of cadaveric grafts to fail and the remainder to have significantly more thinning and elongation than inlay grafts (132,161). Numerous presentations at national meetings and at least one publication (123,161) have confirmed the benefits of the inlay PCL reconstruction. While there is no question that good results can be obtained using the transtibial tunnel endoscopic PCL reconstruction technique, recent evidence suggests the inlay technique more closely recreates the original anatomy of the PCL.
Hinged Knee External Fixation
A new concept in the reconstruction of knee dislocations involved the use of a hinged external fixator (Compass Knee Hinge) and early motion following surgical reconstruction of the knee. A preliminary report indicated that less than 10% of patients using the hinge had any ligament instability following early motion rehabilitation, compared to approximately 40% of patients treated with a conventional brace (114). The data are very preliminary but hold great promise for patients with marked knee instability. Indications for the use of the hinged external fixator combined with early motion following reconstruction include KD-III, KD-IV, and KD-V knee dislocation patterns.
Posterolateral Corner Repair Versus Reconstruction
The conventional wisdom has been that the posterolateral corner should be repaired if surgery is accomplished within 3 or 4 weeks of injury and the tissue quality appears good. However, there were no published series supporting that view. Stannard et al recently presented a series (152) that compared repair using suture anchors to bone with a modified two-tailed reconstruction technique that recreates the popliteus, popliteofibular, and fibulocollateral ligaments. Both groups underwent early motion rehabilitation. The authors found a significant improvement in stability of the posterolateral corner with reconstruction compared to repair. These findings may not occur if early motion rehabilitation is not used, or if alternative repair techniques are used.
Fracture-dislocation of the knee is an uncommon injury that is difficult to recognize without experience and careful evaluation of the knee injury. The term “fracture-dislocation” was coined by Tillman Moore in his 1981 article describing the long-term follow-up of such injuries (94). The hyphenated term may be a misnomer in some circumstances, as such patterns may involve a subluxation rather than a complete dislocation, but the usefulness of the term “fracture-dislocation” is to underline three important concepts involved in this injury type: (1) the ligamentous involvement in what would otherwise be considered only a fracture, (2) the increased risk and potential for arterial injury, and (3) what is otherwise a significantly unstable fracture pattern requiring careful attention to fracture fixation and thoughtful consideration regarding ligament injury management. Since such injury types may mimic a tibial plateau fracture or an isolated avulsion injury, the diagnosis is often overlooked. Although the pattern was initially described as one involving a fracture of the proximal tibia, we have reported on the occurrence of fracture of the femoral condyle in association with a ligamentous injury creating a fracture-dislocation of the knee. The term “femoral-sided fracture-dislocations” is used to more accurately describe this femoral injury type. Such femoral-sided fracture-dislocations produce a fracture fragment described by the AO group as a Hoffa-type fragment (ie, isolated condylar fracture occurring at the level of Blumensaat’s line and with minimal soft tissue attachments). Such fragments are uniquely covered with articular cartilage with a broad surface of cancellous bone in the area of the fracture site (108). Regardless of the side of the knee involved, fracture-dislocations are an interesting complex of injuries that require the orthopaedic surgeon to plan treatment of both fracture and soft tissue (ligamentous) injuries. Adding the risk of arterial injury requires the clinician to tailor the treatment plan to the specific injury as well as to the overall condition of the patient. With fracture-dislocations, the surgeon must think at times not only like a fracture surgeon but also like a sports medicine surgeon to properly treat the ligamentous involvement.

Principles of Management
Mechanism of Injury
Fracture-dislocation of the knee usually involves high-energy trauma as is seen with motor vehicle accidents, falls from heights, and high-energy direct blows to the knee. Fracture-dislocations involving primarily the tibial side of the joint are due to a combination of high energy and valgus or varus rotational forces across the knee. The level of energy affects and defines the injury, with worsening soft tissue injury, displacement, and vascular risk with increasing levels of injury (53).
Femoral-sided fracture-dislocations involve an additional mechanism of injury to that seen with tibial-sided injuries. As will be discussed below, such injuries on the femoral side involve a particular fracture of one or both femoral condyles occurring at the level of Blumensaat’s line. Such fracture patterns rarely occur without a specific force directed at the condylar edge. Furthermore, in our experience such direct blows are from metal objects with a well-defined edge, such as a piece of angle iron, large-gauge steel attached to a vehicle, or that used in building construction (i.e., a steel beam). The object is defined enough to fracture the femur at the specific point such that a shaft fracture does not occur, and dull enough that laceration of soft tissues occurs only with high-energy and large displacements. Knee position is usually at 90 degrees of flexion, allowing the condyle to be relatively exposed, and thus shearing of the condyle, as a Hoffa fragment, occurs. With continued translation, knee ligaments are injured.
Signs and Symptoms
The patient with a fracture-dislocation of the knee usually experienced high-energy blunt trauma and has symptoms and findings consistent with a combined fracture and soft tissue injury about the knee. Patients will complain of varying degrees of pain, an inability to ambulate, swelling, and, depending upon the degree of associated injury, possibly even compartment syndrome-like pain with variable, but less common, sensory disturbances. Both tibial- and femoral-sided fracture dislocations may present with less severe than expected symptoms of pain with lesser degrees of displacement and joint surface involvement. Lastly, patients with a fracture-dislocation can have either an isolated injury or multiple musculoskeletal and/or systems injury, and the degree of overall trauma must be taken into consideration in the evaluation and treatment of the knee injury itself.
Clinical findings of gross global knee swelling are common. The patient may present with deformity, but routinely patients will be noted to have findings of instability patterns in either the coronal or sagittal plane, or both. Tibial-sided fracturedislocations commonly have a varus/valgus instability pattern that may be associated with gross crepitus as the fracture edges move. Specific caution when examining patients with such patterns should be used. X-rays should be inspected prior to carrying out a physical examination, and with such knowledge, examination under fluoroscopy in the presence of large fracture fragments can be very useful. Instability patterns suggestive of a cruciate ligament injury are also common but must be interpreted carefully. Both Lachman and posterior drawer examinations can be grossly positive, but the cruciate ligaments may be intact and, with fracture stabilization, knee instability will normalize. The femoral-sided fracture-dislocation involving the medial femoral condyle is one common example of this situation where the PCL bundles move with the fracture fragment, and stabilization of the “Hoffa-like” fragment anatomically reestablishes normal PCL function. Nonetheless, midsubstance injuries to the cruciates do occur with the fracture-dislocation injury, and thus the clinical examination frequently must be combined with a secondary imaging study (we find MRI to be more useful in fracture-dislocations than CT) to clearly understand the ligamentous injury prior to creating a treatment plan.
As discussed in the knee dislocation section above, examination of a traumatized knee is often difficult and in our experience involves EUA. EUA is clearly an important step, as simply positioning the knee at 90 degrees of flexion may be impossible on initial clinical examination without anesthesia. Certainly patients sustaining multiple trauma who require emergent stabilization or treatment for life-threatening systemic, open, or vascular injuries can undergo EUA near the time of presentation. In patients with an isolated injury, examination should be performed with care and limited by the clinician as to the amount of pain created. Use of short-term reversible analgesics and anxiolytics can be extremely effective and allow the orthopaedic surgeon to obtain a clear understanding of the degree and type of injury. Lastly, an MRI without EUA can be difficult to interpret, as the MRI will tend to “overcall” ligamentous injury. Although we feel MRI is extremely important in the evaluation of both knee dislocations and fracture-dislocations, the functional integrity of a ligament requires the critical information derived from EUA.
Fracture-dislocations of the knee involve a significant risk to the vascular tree about the knee (53). Not only can direct injury to the popliteal artery and vein occur with a fracture-dislocation, but also a compartment syndrome of the leg may occur and should be a consideration in the initial evaluation of the injured patient. Such associated injuries require the evaluation of an experienced clinician with a high degree of clinical suspicion.
Associated Injuries
The fracture-dislocation, when recognized, should direct the clinician to suspect other injuries to the surrounding soft tissues about the knee. Much like a knee dislocation, the fracturedislocation can involve a vascular injury, a neurologic abnormality (especially of the peroneal nerve), disruption of the soft tissue envelope (especially an open injury), and damage to the extensor mechanism.
Vascular injuries occur in fracture-dislocations much in the same way as with pure ligamentous knee dislocations. The combination of fracture and dislocation allows for unchecked displacement between Hunter’s canal and the soleus arch, which directly puts the popliteal artery at risk. Furthermore, the sharp

edge of the proximal tibial fracture can directly lacerate or kink the vessel, creating vascular insufficiency. The vascular management of the fracture-dislocation is much the same as for the dislocated knee. Palpating the pedal pulses is the first step, and vascular consultation should be obtained. Because of the complexity of both bone and ligamentous injury, a strong argument for arteriography can be made even with a clinically normal vascular examination. Knowing the status of the vessels is critical for proper treatment. Certainly vascular insufficiency has clear-cut steps in management that involve emergent vascular exploration. In such injuries, the location of the fracturedislocation localizes the area of arterial injury; ironically, arteriography may not be required in such limb-threatening presentations, with the vascular surgeon proceeding directly to arterial exploration and repair. Clearly, the time required for revascularization cannot be delayed past 6 to 8 hours, after which the risk of limb loss approaches 80% due to insufficient arterial collaterals about the knee. The orthopaedic surgeon is placed in a precarious position in such injury patterns. Vascular surgery approaches differ between institutions as well as among vascular surgeons (although we prefer the posteromedial approach for vascular repair in a fracture-dislocation of the knee, some vascular surgeons prefer a direct posterior approach). The treating orthopaedic surgeon should become familiar with his or her vascular surgeon’s preference and develop a good working relationship through direct communication to ensure a wellconceived treatment plan for the patient with a combination of knee instability and vascular insufficiency.
Vascular repair has been described using two different approaches, posteromedial and direct posterior. Both approaches have proponents and, depending upon the vascular surgeon (or institution) involved, the choice is usually made outside of the orthopaedic surgeon’s purview (79,162). Nonetheless, our preference is the posteromedial approach, usually in combination with external fixation for knee fracture-dislocation stabilization. The posteromedial approach is extensile; it can be performed with the patient in a supine position; it allows ease of positioning of the knee in flexion or extension; and it allows relative access to the front and back of the knee. The posterior approach, in contrast, is performed in the prone position, is nonextensile, requires a change in patient position to place external fixation, requires the knee position angle to be held or bolstered, and allows access only to the posterior aspect of the knee. Although on first thought access to the PCL would seem to be an advantage of the straight posterior approach, there is poor access to the femoral origin of the PCL and virtually most of the knee. Lastly, the complexity of the posterior approach, involving identification of the neural bundles, in our opinion tilts the scales to a posteromedial approach. But as noted above, each particular institution will have certain nuances of vascular care that are best worked with rather than against.
Neurologic injuries are relatively common, especially those involving unchecked varus rotation causing a peroneal nerve traction injury. Tibial nerve involvement, although relatively less common, usually implies a more serious condition such as a compartment syndrome rather than the traction-type injury seen with the peroneal nerve. Patients with tibial nerve symptoms should be carefully evaluated for compartment syndrome prior to making the diagnosis of a simple traction injury. With respect to peroneal nerve involvement, one of us has pursued exploration and neurolysis of the peroneal nerve; this experience has seen rapid return of peroneal function while allowing simultaneous treatment of the posterolateral ligamentous structures.
Open injuries do occur and require immediate debridement and irrigation. Use of temporary spanning external fixation allows for relatively quick immobilization and easy access to wound management. Fracture-dislocations of the knee can have certain fracture patterns, such as a large condylar fragment, which may be readily exposed at the time of soft tissue debridement. Depending upon the degree of soft and hard tissue contamination, simultaneous fracture fixation at the time of irrigation and debridement may be entertained. Nonetheless, with greater degrees of complexity of injury and contamination, the clinician should more strongly consider initial stabilization with spanning external fixation and pursue definitive reconstruction later. Certainly, combinations of both techniques at the time of surgery may be required (Fig. 51-25). In the presence of an open injury, the clinician can evaluate the knee both with EUA as well as with stress fluoroscopy. With an external fixator in place, MRI can be poor and CT may be required for better definition of the fracture fragment(s).
There is little in the literature concerning the treatment of knee fracture-dislocations (53,94,163). Nonetheless, the recommendations from the Los Angeles County experience involve two critical components of treatment: (a) stable fracture fixation and (b) ligamentous repair. Although it is a quarter of a century after Tillman Moore’s initial clinical description, treatment recommendations are relatively the same (94). While the clinician may consider a ligament reconstruction rather than repair, the concept of treating both the fracture and ligament injury remains sound to this day. In addition to the surgical method, carefully monitored protected weight-bearing is required for 10 to 12 weeks after surgery.
Fracture fixation depends on the pattern present and differs significantly between the tibia and the femur. Fixation of tibial-sided fracture-dislocations involves classic stable plate and/or screw fixation of the injured tibial condyle, with methods usually favoring plate fixation to aid in stability. The emergence of locking plate technology adds greatly to the treatment of such injuries, but its role is still being defined. Certainly, the use of soft tissue-sparing approaches with locking plates has advantages, as does the improved stability of fixation afforded by these devices. Anatomic fixation and creation of a stable construct is critical whether achieved with a locking plate mechanism or with standard nonlocking plate fixation. The femoral-sided fracture-dislocation presents with a more difficult fracture pattern than the tibial-sided injury. The femoral-sided injury is usually


that of an all-articular fracture fragment at the level of the Blumensaat’s line (Hoffa fragment). Fixation of such a fragment requires transarticular screws, and use of a plate is not feasible. Use of bone graft or bone graft substitutes is often necessary in combination with fracture fixation. A displaced lateral condylar tibial fracture often presents with moderate to severe fracture impaction and bone loss that with fracture surface reduction leaves a bony defect. Bone grafting of such defect sites should be considered. Regardless, the fracture-dislocation is highly unstable and requires stable fracture fixation following AO principles.
FIGURE 51-25 A 14-year-old was struck by a drunk driver and sustained an open midshaft femur fracture, a supracondylar femur fracture, and a comminuted proximal tibial fracture. A. Close-up of open knee wound. B. Sagittal split fracture of proximal tibia with shaft disassociation. C. AP x-ray showing the supracondylar femur fracture. D. After debridement, initial joint surface fixation was acquired with two screws, and a spanning external fixator was applied. E. Definitive fixation of the femur fracture was acquired at 10 days using two retrograde fixation nails. The proximal tibial fracture was stabilized with a hybrid frame. Ten days later a gastrocnemius flap was performed. F. Radiographic appearance of the healed fractures at 6 years. (Copyright Robert C. Schenck, Jr. Albuquerque, NM. Reprinted with permission.)
Diagnosis and Classification
Certainly the most commonly used classification of the proximal tibial fracture-dislocation is that published by Moore. It includes five types: type 1 (split), type 2 (entire condyle), type 3 (rim avulsion), type 4 (rim compression), and type 5 (four-part). Types 1, 2, and 5 involve a fracture of the medial tibial condyle and are highly unstable. Types 3 and 4 can be readily identified radiographically. This classification, in our opinion, continues to accurately describe the most commonly seen injury patterns of the tibial fracture-dislocation (Fig. 51-26).
Type 1 or split fracture-dislocations of the proximal tibia occur only in the medial condyle, usually with no comminution. The fragment occurs in the coronal plane, displaces distally, and frequently gives a double shadow line in the medial compartment on the anteroposterior x-ray. The fracture pattern presumably occurs in knee hyperflexion and in Moore’s series rarely resulted in arterial injury.
Type 2 or entire condyle fracture-dislocations of the proximal tibia mimic the Schatzker type IV pattern but have a fracture line lateral to the tibial eminence that exits medially in the sagittal plane at approximately 45 degrees to a large condylar fragment. The fracture pattern lateral to the eminence and distal to the insertion of the tibial collateral ligament produces an instability pattern of the knee equivalent to a tear of both cruciates and the MCL. Both peroneal nerve and vascular injury rates are significant in this pattern.
Type 3 fracture-dislocations have an avulsion type fracture in which the fragment (joint edge or “rim”) is raised from its normal position and occasionally rotated. The avulsion fragment is large and involves either the lateral plateau or both the lateral tibial plateau and the proximal fibula. There is a significant risk of both peroneal nerve and popliteal artery injury in this fracture-dislocation pattern.
Type 4, or rim compression, differs from the rim avulsion by the radiographic appearance with the fragment being located either distal to the normal anatomic position or the rim being crushed or comminuted. The mechanism of injury occurs secondary to a direct blow from a moving vehicle. With involvement

of the lateral plateau, there is frequently injury of the anterior tibial spine. Contralateral involvement of the collateral ligament is likely with this type of fracture (Fig. 51-27).
FIGURE 51-26 Classification of fracture dislocations of the knee. (Redrawn after Moore TM. Fracture-dislocation of the knee. Clin Orthop 1981;156:128–140, with permission.)
Type 5 (four-part) fracture-dislocation involves a median eminence fracture with separation or discontinuity of the tibial shaft and the condyles. This distinguishes it from a bicondylar fracture or even a Shatzker type VI proximal tibia fracture. A shift of the femur from the lateral aspect of the proximal tibia is usually seen, defining the injury as a fracture-dislocation.
Careful assessment of the fracture is critical, especially to determine the type of fixation required, but the type of ligament injury is just as important. Ignoring the ligamentous injury can lead to loss of fracture fixation and collapse. Although Moore’s classification discusses mostly fracture patterns, his approach involved treatment of both the fracture and the ligament injury. This approach we believe still holds true. The evaluation of the fracture-dislocation requires careful definition of the ligaments involved, and doing so can add tremendous information to the Moore classification system. To achieve this, fracturedislocations most frequently require EUA, especially once the fracture has been internally fixed. MRI, although not a functional examination of the ligaments, is also extremely useful in assessing the injury. Lastly, reevaluation of ligament stability after fracture fixation is critical; doing so may preclude the need for further ligament surgery. For example, with a large medial tibial condylar fragment involving the eminence, fracture fixation may often normalize the cruciate examination once the cruciate insertion sites have been stabilized.
FIGURE 51-27 In this type 4 fracture-dislocation, the rim of the medial plateau is crushed and the lateral collateral ligament mechanism is disrupted, as shown on a valgus stress film of the knee.
FIGURE 51-28 Unicondylar femoral-sided fracture-dislocation, with a locked complex dislocation. (Copyright Robert C. Schenck, Jr. Albuquerque, NM. Reprinted with permission.)
The femoral-sided fracture-dislocation is rarer than tibial-sided fracture dislocations and it is best described in one of six patterns:
  • UC.1: Unicondylar, either medial or lateral femoral condyle fractured
  • UC.2: Unicondylar, with a locked condyle, a complex fracture-dislocation (Fig. 51-28)
  • UC.3: Unicondylar with disruption of the extensor mechanism
  • BC.1: Bicondylar fracture
  • BC.2: Bicondylar fracture, with one or both condyles locked, a complex fracture-dislocation
  • BC.3: Bicondylar fracture with disruption of the extensor mechanism.
As with any fracture-dislocation with arterial or neurologic involvement, the subscript C or N, respectively, should be added to this descriptive classification.

Femoral-sided fracture-dislocations have varying types of ligament involvement. Specific to the medial femoral condyle fracture, the PCL is usually well attached to it and uninjured, and EUA will reveal a gross posterior sag that normalizes after reduction and fixation of the fractured medial femoral condyle. With displaced femoral condyle fractures, the ligament examination can be difficult to perform initially and frequently requires a repeat EUA once the fracture is reduced and fixed. With the displaced and locked condyle fracture, determining the specific condyle that is injured can be difficult on plain x-rays alone due to the overlap of the condyles on the lateral as well as the rotated x-ray views initially obtained at the time of evaluation in the emergency room. Use of a secondary study, especially an MR or CT scan, can provide much preoperative information regarding the fracture and the ligaments involved.
Surgical and Applied Anatomy
For proper management of the fracture-dislocation, attention must be given in particular to the normal anatomy of the tibial and femoral condyles. The femoral condyles are asymmetric in size and shape. The medial femoral condyle is approximately 1.7 cm longer than the lateral condyle in its outer circumference. This asymmetry in length produces axial rotation of the tibia on the femur during flexion and extension (4). With regard to width, the lateral condyle is slightly wider than the medial when measured at the center of the intercondylar notch. In the sagittal axis of the knee, the lateral femoral condyle is longer or more anterior than the medial condyle. In the coronal or anterior-posterior plane, the medial femoral condyle projects further distally than does the lateral condyle (5,6). When the femur is viewed along its anatomic axis, this appearance becomes obvious. However, in normal weight-bearing alignment, the condyles appear to be equal in length. The parallel condylar surfaces are created by the mechanical axis configuration of the lower extremity.
The tibial plateau joint surface is complex. The normal tibial articulation involves the menisci to provide congruity to the distal femoral condyles, and in reality the menisci should be considered tibial extensions. The menisci function to create conformity between the flat tibial and curved femoral surfaces. The medial condyle of the tibia is nearly flat and has a larger surface area than the lateral condyle. The lateral condylar surface is slightly concave. Both condyles have a 10-degree posterior inclination to the tibial shaft in the sagittal plane. Bordering the notch are the tibial spines (or tubercles), both medial and lateral, which function to stabilize the condyles from side-to-side motion. The interspinous area is void of hyaline cartilage and is the insertion site for the meniscal horns and the cruciates. The cruciates insert on the intertubercular sulcus and not on the spines themselves (5,6,11,164,165). Due to the asymmetry of the tibial condyles and the relative covering of each respective meniscus, the medial tibial plateau does not tolerate joint surface incongruity as well as the lateral tibial plateau does. With the more extensive covering of the lateral meniscus, up to 5 to 10 mm of lateral plateau displacement may be tolerated clinically, depending upon the exact configuration of the fracture. Although anatomic reduction is considered the goal in fracture management, the clinician should remember the differences specifically between the medial and lateral tibial plateaus.
The anatomy of the popliteal neurovascular structures explains their susceptibility to injury. The popliteal artery and vein course from the fibrous tunnel of the adductor hiatus through the popliteal space (giving off the five geniculates) and exit through the fibrous arch of the soleus muscle. Being securely fixed proximally at the adductor hiatus and distally at the soleus arch, the popliteal artery and vein can be torn or stretched with the exaggerated tibiofemoral displacement or hyperextension that produces the dislocation.
Surgical treatment of knee fracture-dislocations frequently involves the use of open approaches. Although the lateral compression type of injuries with an associated contralateral ligament injury can be treated with arthroscopic-assisted approaches, the clinician is usually faced with a large condylar fragment, gross capsular disruption, and the need to openly reduce the fracture fragment. Furthermore, with acute injuries to both the condyle and ligament, the risk of arthroscopic fluid extravasation is a concern, as it can result in a compartment syndrome or vascular insufficiency. Certainly delayed ligament reconstruction is best performed with arthroscopic approaches; in contrast, early surgery involving fracture fixation and frequently ligament treatment requires an open approach. Selection of the specific approach depends upon the fracture configuration and ligaments involved; treatment may require the use of combined incisions. In such scenarios, the maintenance of an adequate soft tissue bridge between incisions must be kept in mind. The posteromedial, posterolateral, and anterior approaches are commonly used in the treatment of these fracture-dislocations.
Table 51-6 Treatment of Knee Fracture-Dislocation
Treatment Options Advantages Disadvantages
Open surgery
  1. Allows for stable reduction
  2. Collaterals can be approached
Higher risk for stiffness, especially with immobilization
Arthroscopic surgery Minimizes soft tissue injury
  1. Higher risk for extravasation of arthroscopic fluid
  2. Collateral ligament repair is delayed
Immediate cruciate reconstruction Early stability Higher risk of stiffness

Current Treatment Options
Knee fracture-dislocations require a balance of fracture fixation techniques and ligamentous surgery. Due to the relative instability of the fracture-dislocations, stable internal fixation with screws and plates is recommended. When reconstructing tibial-sided fracture-dislocations, the clinician should be wary of using cannulated screw fixation as the sole fixation, especially for the large medial tibial condyle fractures. Such fixation is excellent for reestablishing the joint surface, but it should be augmented with condylar plate fixation, with locked or unlocked screw-plate interfaces. With isolated cannulated screw fixation of a large medial condylar fracture, the injury will frequently displace and angulate due to the high varus angular forces that will be applied postoperatively. Ligament surgery involves multiple options but should be used within each fracture-dislocation pattern with care. Cruciate injury usually is an avulsion that can be easily repaired surgically. Cruciate reconstructions, in general, should be delayed to avoid arthrofibrosis (Table 51-6).

Pearls and Pitfalls
Knee fracture-dislocations are somewhat variable in presentation and severity, and for that reason they require an individualized approach depending upon the soft tissue envelop, fracture geometry, ligament involvement, vascular status, and overall patient condition.
  • Use techniques of treatment with which you are familiar. When forming a preoperative plan for a relatively rare injury type, consult a more experienced surgeon to assist in the plan and even the surgery itself. Obtain as much information as possible with an EUA and a secondary imaging study, either MRI or CT, once vascular injury is ruled out and prior to definitive reconstructive surgery.
  • Protect the soft tissues. Use short-term immobilization with a bulky Jones splint with frequent vascular checks. Reevaluate the leg compartments.
  • Educate your patient. The complexity of such an injury will not be obvious to the patient and family. If the patient allows, involve the family in this education progress. The family will remember more clearly the details, especially if the patient has a complication you had previously discussed.
  • Get your vascular surgeon involved here early and always. Know your institution’s vascular protocol; if one isn’t present, establish institutional guidelines. Such guidelines will protect you in the middle of the night. Do not isolate yourself in the vascular decision making; always obtain a consultation. Clearly communicate the orthopaedic plan to your vascular surgeon, as he or she may have little background information on the orthopaedic injury. Your insight and direction will be invaluable to the vascular surgeon. Try to place the external fixator before the vascular repair, but do not be surprised if the vascular team wants you to wait until they have reestablished flow to the leg. Assist the vascular team in the four-compartment fasciotomy. As orthopaedic surgeons we have tremendous experience in this area that will be appreciated by the vascular team. Carefully plan with your vascular surgeon the timeline to mobilization of the knee joint after arterial repair.
  • Use only stable internal fixation. Fracture-dislocations are highly unstable and will tend to displace, especially with weight-bearing. Obtain intraoperative plain x-rays to critically evaluate the reduction, fixation, and screw placement. Always reevaluate the ligament injury after fracture fixation to determine the need for further ligament surgery.
  • Reconstruct or repair the collateral ligament complex at the time of fracture fixation if varus or valgus stability persists once a stable fixation has been performed. Delay cruciate ligament reconstructions. Simultaneous open surgery, cruciate reconstruction, and immobilization are a recipe for severe permanent postoperative stiffness and heterotopic ossification.
  • Avoid trying something new in the middle of the night, if possible. Delay a challenging reconstructive effort for the best time of day for you and the operating room staff. Hence, use short-term spanning external fixation to obtain initial stability, especially when there is gross instability, an open wound, or a vascular injury. Occasionally work is required at night due to open or vascular injuries. In such scenarios, avoid any delay. Examine the ligaments under anesthesia and do not rely solely on the MRI.
  • Avoid transverse incisions. Use longitudinal incisions with a large skin bridge (7 to 9 cm at a minimum) between them. Plan for future reconstructive efforts with your first surgical approach to the knee.
  • Do not forget to warn your patients and, if the patient allows, the family as well. Be detailed in your discussion of potential pitfalls. In our experience, patients want to be educated. Clearly explain the negatives to them.
  • Do not delay vascular consult or vascular treatment. Injuries such as these present frequently at night in the worst of clinical scenarios. Never rely on the concept of spasm as an explanation for poor perfusion, and do not wait for possible collateral flow to offset a vascular injury. If ischemia is present, the limb should be revascularized.
  • Do not immobilize the knee unless it is necessary to protect a vascular repair or an extensive soft tissue repair. If fracture fixation remains unstable, immobilization carries with it a high risk of arthrofibrosis. The combination of a closed head injury and immobilization can frequently produce severe heterotopic ossification. Despite achieving stable fixation and pursuing early range of motion, we advise our patients of a need for manipulation in approximately 20% of cases.
  • Do not rely on fluoroscopic images to make final judgments on your fixation efforts. Intraoperative plain x-rays show the quality of reduction and fixation best and allow the surgeon to make a more accurate assessment of fixation and joint position.
  • Do not reconstruct the cruciates early unless necessary. Focus on the fracture and collateral and corner ligament management. Delayed cruciate reconstruction can follow once motion is reestablished and the fracture has healed.
Knee fracture-dislocations are significantly prone to complications ranging from the short-term problems of vascular risk and resultant loss of limb to chronic instability, stiffness, heterotopic ossification, and subluxation. Much like knee dislocations, the presence of a peroneal nerve palsy is a chronic functional problem that to this day remains difficult to treat and is described in detail in the knee dislocation section above.
It is essential to avoid vascular insufficiency and limb loss, but despite aggressive vascular evaluation occasionally the injury is nonsalvageable. The patient presenting with vascular injury and a severe nonreconstructable tibial nerve injury requires

consideration for early amputation. Such a decision requires a team approach with careful documentation preoperatively and intraoperatively. The need for an above-knee amputation in selected circumstances and its relatively poorer functional recovery compared to a below-knee amputation adds to the complexity of the treatment decision of salvage versus amputation. Certainly the patient presenting with a concomitant reconstructable vascular injury requires an aggressive approach of minimally delayed vascular repair or reconstruction and joint stabilization. Use of spanning external fixation to stabilize the knee and vascular repair combined with four-compartment fasciotomies after reestablishing arterial flow can minimize long-term functional loss. In our experience, having a well-versed orthopaedic and vascular team with all members in communication avoids delays in treatment and allows for coordinated care. As with managing any arterial injury, the attention to time with its proper documentation in the medical record is extremely important. Certainly thinking in terms of a 6- to 8-hour timeline facilitates the management of such patients.
Arthritis, stiffness, and heterotopic ossification frequently are seen together, although arthritis usually presents years after the initial injury. Arthrofibrosis can be a significant problem that is difficult to manage after a fracture-dislocation of the knee, especially in the context of severe heterotopic ossification. Although loss of both extension and flexion occurs, in our experience the flexion contracture is often more disabling. Certainly, stiffness should be aggressively managed with postoperative physical therapy, but this can still be confounded by the need for the patient to remain non-weight-bearing for 10 to 12 weeks while the fractures heal. Once fracture healing has progressed to allow weight-bearing, further aggressive range-of-motion exercises should be instituted, including passive stretching in extension, flexion on a stationary bike with an elevated seat, as well as gait retraining so that the patient returns to a normal heel-toe gait. The effectiveness of manipulation and arthroscopic lysis of adhesions under epidural anesthesia is well documented (120). Unlike stiffness in the dislocated knee with a cruciate injury, the clinician may be required to wait for clinical fracture healing to occur prior to proceeding with a manipulation under anesthesia and lysis of adhesions. Following the acute injury repair, close patient follow-up is required to identify a plateau of motion that resists further physical therapy intervention. In our experience, knee dislocations should be given a maximum of 6 to 8 weeks prior to manipulation, whereas fracture-dislocations may require a longer period of observation to avoid fracture displacement.
In one study of knee dislocations at a level I trauma center, ankylosing heterotopic ossification occurred in 16% of patients and was correlated with the presence of a closed head injury and an Injury Severity Score of greater than 25. In our experience, despite aggressive efforts at range of motion, stiffness and heterotopic ossification occur occasionally and result in “a knee of stone” that is particularly recalcitrant to any treatment. Although heterotopic ossification and stiffness are common after knee dislocations and fracture-dislocations, there are no current recommendations for perioperative radiation or pharmacologic treatments.
Arthritis after knee fracture-dislocation can occur due to stiffness (with resultant patella baja), articular injury, or articular incongruence. Often it is difficult to separate the etiologies as to a specific cause. The need for a future osteotomy or knee replacement surgery should be kept in mind with the initial operative approach so that an incision appropriate for future treatment (ie, an anterior longitudinal incision for a total knee replacement) is available.
Lastly, late ligamentous instability is occasionally seen and is usually accompanied by a combination of fracture collapse or displacement. Such patients rarely have associated stiffness, and a combination of ligament reconstruction and osteotomy is frequently required. The presence of isolated cruciate instability is more easily treated and can be approached using arthroscopic-assisted techniques. Frequently the presence of hardware about the condyles requires partial or complete removal to create femoral or tibial tunnels or inlay sites. Evaluation of such patients requires careful observation of the gait for a limp or thrust or the presence of a flexion contracture. Full-length weight-bearing x-rays, and occasionally stress x-rays, are required for complete understanding of the insufficient structures, be they bone or ligament. As a general rule, an unstable knee is better tolerated than a stiff knee, especially a stiff knee with a flexion contracture.
Controversies/Future Directions
Knee fracture-dislocations are rare and require further long-term study. In patients with tibial- or femoral-sided fracture-dislocations, the long-term prognosis remains guarded. The role of ligament repair versus reconstruction for both the posteromedial and posterolateral corner involvement will become clearer, and now the trend appears to be drifting toward reconstruction for optimal stability and function. Locking plate technology has the potential to greatly add to the treatment of fracturedislocations to allow earlier and more aggressive range of motion, as well as earlier weight-bearing. Both outcome and treatment options will become better defined but will in all likelihood continue to involve the time-tested approach of stable fracture fixation and the reestablishment of ligament function.
Injury to the proximal tibiofibular joint is an uncommon injury, and it is even less common as an isolated injury. The first description of a proximal tibiofibular joint injury was by Nelation in 1874. In a review performed in 1974, only 100 such cases were identified in the literature (66,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182). The dislocation may be isolated (particularly associated with horseback or parachuting activities) or may be only one part of a complex high-energy injury of the lower extremity.

Principles of Management
Mechanism of Injury
The tibiofibular joint is inherently stable due to its articular anatomy, ligament support, and protected position lying on the tibia. Added stability comes from the LCL with the knee positioned in extension. Thus, dislocation of the proximal tibiofibular joint requires the knee to be in a flexed position. Dislocation of this joint occurs with high-energy trauma and is reported in association with posterior hip dislocation (flexed knee and hip), open tibia-fibula fractures, and other fractures about the knee and ankle. Gross and usually posterior dislocation is associated with such violent trauma (11,183,184). Isolated dislocations occur from sporting injuries with an associated exaggerated twisting injury. Larson (185) noted a posterior dislocation to occur with ankle inversion and peroneal muscle spasm. Ogden (173,186) described four patterns of injury of the tibiofibular joint, one of subluxation and three of dislocation (anterolateral, posteromedial, and superior). In his review of 43 cases, 10 patients presented with subluxation, 29 with an anterolateral dislocation, 3 with a posteromedial dislocation, and 1 with a superior dislocation. Injury occurred most commonly during the second to fourth decades of life (Fig. 51-29).
Signs and Symptoms
The patient presents with pain on the lateral side of the knee and, if the injury is isolated, with a history of the knee being in a flexed position. Severe trauma to the knee or lower extremity can also be present when a dislocation occurs as an associated condition. In such multitrauma the diagnosis is usually made radiographically and is minimized due to the gravity of the associated injuries. With an isolated injury, the diagnosis more commonly presents as a knee injury from a violent twisting injury or a direct blow, as from the bumper of a motor vehicle (186,187). In such a presentation, physical examination reveals tenderness around the fibular head. Comparison of both knees with palpation of the normal anatomic landmarks (fibular head, Gerdy’s tubercle, lateral femoral epicondyle, tibial tubercle) and their relative positions can clarify the diagnosis on physical examination alone.
Radiographic findings can be confusing, as there is difficulty in patient positioning secondary to discomfort and in obtaining comparison views of the normal knee. Comparison views are essential, and in patients with equivocal findings CT will clearly identify the presence or absence of dislocation and will give the added opportunity to study the normal contralateral tibiofibular articulation. In the most common pattern of an anterolateral dislocation, the fibula is positioned lateral to the tibia on an anteroposterior x-ray of the knee (Fig. 51-30). Associated injuries are rare, but the peroneal nerve can be injured.
Rationale, Diagnosis, and Classification
The literature on this injury pattern is replete with isolated case reports. The classic description of injury to this joint by Ogden

in 1974 also includes 50 cadaver dissections of the articulation and its ligamentous anatomy (186). The study revealed two types of tibiofibular articulations: oblique and horizontal orientation of the articular surfaces (Fig. 51-31). The horizontal joint surface is transverse to the long axis of the tibia (parallel to the floor in a standing position) and when the orientation of the joint is more than 20 degrees away from the horizontal, it is classified as oblique. The articular surface area is decreased in the oblique joint pattern. The ligamentous support of both joint types includes a thickened joint capsule, with condensations anteriorly and posteriorly. Anteriorly a ligamentous band runs from the fibula to the tibia. Posteriorly there is a thickened band from the tibia to the fibula that has a contribution from the popliteus tendon. Cutting studies performed by Ogden revealed stability of the joint to be present unless the fibular collateral ligament was cut or the knee was flexed past 80 degrees.
FIGURE 51-29 Ogden classified anomalies of the proximal tibiofibular joint into subluxations and three types of dislocations: anterolateral, posteromedial, and superior. (Redrawn after Scott WN. Ligament and extensor mechanism injuries of the knee: diagnosis and treatment. St. Louis: Mosby-Year Book, 1991, with permission.)
FIGURE 51-30 X-ray appearance of an anterolateral proximal tibiofibular joint dislocation (A) and subsequent reduction (B). (From Scott WN. Ligament and extensor mechanism injuries of the knee: diagnosis and treatment. St. Louis: Mosby-Year Book, 1991, with permission.)
FIGURE 51-31 Two types of the proximal tibiofibular joints, oblique and horizontal, as described by Ogden. (Redrawn after Scott WN. Ligament and extensor mechanism injuries of the knee: diagnosis and treatment. St. Louis: Mosby-Year Book, 1991, with permission.)
Surgical and Applied Anatomy
The tibiofibular articulation is posteriorly positioned on the lateral aspect of the knee and can be palpated subcutaneously in this area. The peroneal nerve is palpated just distal to the joint on the posterolateral aspect of the fibular neck approximately 3 cm distal to the lateral tibiofemoral joint line. Rarely is an open approach or stabilization required to treat dislocations of the proximal tibiofibular articulation. If such is required, isolation of the peroneal nerve prior to reduction is necessary to avoid injury during exploration and repair of the dislocation.
Current Treatment Options
Reduction is usually simple; it can be performed closed and is dependent upon the direction of displacement. The physician applies a force opposite to the position of dislocation directly on the fibular head with the knee in a flexed position. An audible snap is usually heard at the time of reduction, and

the joint reduction is stable. The superior dislocation requires a distally directed force applied to the proximal fibula in the area of the insertion of the fibular collateral ligament, with a simultaneous addition of ankle inversion. Immobilization of the knee should only be temporary. Although non-weight-bearing has been recommended initially for 2 weeks, rapid functional return with weight-bearing occurs once tenderness of the joint resolves.
Table 51-7 Treatment of Dislocation of the Proximal Tibiofibular Joint
Treatment Options Advantages Disadvantages
Closed reduction Commonly successful Minimal
Open reduction Necessary for a complex dislocation Risk to peroneal nerve
Proximal tibiofibular fusion Rarely indicated Occasional long-term disability after fusion
Resection May be used to treat chronic instability Compromises fibular collateral ligament
Complex or irreducible dislocations are rare, and open reduction is thus not frequently required. Several stabilization methods have been reported, including pin fixation, fusion, and proximal fibular resection, but these are best avoided in the acute setting. Parkes and Zelko recommended open reduction and pin fixation using Kirschner wires and immobilization for 6 weeks, after which the pins are removed and range of motion is started (176). Arthrodesis of the proximal joint has been associated with long-term difficulties about the ankle, including pain (184). Resection has been successful to treat chronic instability of the proximal tibiofibular joint or peroneal nerve symptoms but should be cautioned against in the acute situation (Table 51-7).
Long-term results of the closed treatment of dislocations are good. Arthritis rarely occurs and, due to the normally limited range of motion of this joint, it is usually minimally symptomatic. Peroneal nerve symptoms are the most common acute complication, and they usually resolve with joint reduction. Peroneal nerve dysfunction is usually seen with posterior dislocations, and Lyle reported peroneal palsies in up to 5% of tibiofibular dislocations (171,174). As with the reduction of any joint, nerve function that worsens with manipulation or following reduction requires exploration of the nerve.
Controversies/Future Directions
This relatively rare injury is usually treated effectively by closed means with good long-term results. Care should be taken not to overtreat this injury.
We thank Sandy Mosher, Dustin Richter, and Joan Stephens for their untiring work in assisting with the chapter.
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