Mm

Figure 53-1 The origin of the posterior cruciate ligament forms an ellipse on the posterior portion of the medial femoral condyle. (From Giffin JR, Annunziata CC, Harner CD: Posterior cruciate ligament injuries in the adult. In DeLee JC, Drez D Jr, Miller MD [eds]: Orthopaedic Sports Medicine, 2nd ed. Philadelphia, WB Saunders, 2003, pp 2083-2106.)

At least one ligament is present in more than 90% of specimens and both are found more commonly in younger patients, suggesting that they may degenerate with age.8,10 These meniscofemoral ligaments are believed to provide significant anatomic and biomechanical stability to the lateral meniscus, although their precise role is not currently well defined.9 The ligament of

Figure 53-2 The posterior cruciate ligament inserts in a central depression called the tibial fovea located 1 to 1.5 cm below the tibial joint line. (From Giffin JR, Annunziata CC, Harner CD: Posterior cruciate ligament injuries in the adult. In DeLee JC, Drez D Jr, Miller MD [eds]: Orthopaedic Sports Medicine, 2nd ed. Philadelphia, WB Saunders, 2003, pp 2083-2106.)

Figure 53-2 The posterior cruciate ligament inserts in a central depression called the tibial fovea located 1 to 1.5 cm below the tibial joint line. (From Giffin JR, Annunziata CC, Harner CD: Posterior cruciate ligament injuries in the adult. In DeLee JC, Drez D Jr, Miller MD [eds]: Orthopaedic Sports Medicine, 2nd ed. Philadelphia, WB Saunders, 2003, pp 2083-2106.)

Figure 53-3 The posteromedial bundle of the posterior cruciate ligament (A-A') is taut in extension and lax in flexion, while the anterolateral bundle (B-B') is reciprocally tight in flexion and lax in extension. (From Giffin JR, Annunziata CC, Harner CD: Posterior cruciate ligament injuries in the adult. In DeLee JC, Drez D Jr, Miller MD [eds]: Orthopaedic Sports Medicine, 2nd ed. Philadelphia, WB Saunders, 2003, pp 2083-2106.)

Humphry is usually smaller than the ligament of Wrisberg, but the strength of each is comparable to that of each other and to that of the PM band of the PCL.8 These ligaments may act as secondary restraints to posterior tibial translation, especially when the knee is flexed. Meniscofemoral ligaments may sometimes be preserved in the PCL-injured knee, making posterior laxity less dramatic.2

Other ligaments about the knee, the lateral collateral ligament, medial collateral ligament (MCL), and especially the PLCC, are secondary stabilizers to posterior tibial translation, playing a minimal role if the PCL is intact but become important if the PCL is deficient.1 In cadaveric studies, if only the PCL is sectioned, an average posterior tibial translation of 11 to 15 mm results; however, if the PLCC is also disrupted, posterior translation approaches 30mm.1,2 Muscle forces about the knee also affect in situ forces on the PCL. Specifically, popliteus and quadriceps contraction can reduce PCL load, whereas hamstring and gastrocnemius contraction increase it.9

ETIOLOGY OF INJURY

Historically, PCL injuries have been underdiagnosed. Recent studies describe PCL tears as accounting for 3% to 20% or more of all knee ligament tears, although still occurring less frequently than injuries of the ACL, MCL, and lateral collateral ligament.1,7,11-13 It is reported that dedicated arthroscopists and orthopedic sports physicians may perform only one tenth the number of PCL reconstructions as ACL reconstructions annually.14

The average age for PCL injury is approximately 30 years old. Athletic injuries account for as many as two thirds of all injuries, with high-energy trauma, especially motor vehicle accidents, accounting for much of the remainder.14 The most common sports in which PCL injury occurs involve high-contact forces, such as rugby and football. Injury occurs less frequently in the cutting and pivoting activities classically associated with ACL injury, such as basketball and soccer. Sporting injuries more fre-

Figure 53-4 The meniscofemoral ligaments arise from the lateral meniscus and run alongside of the posterior cruciate ligament. (From Giffin JR, Annunziata CC, Harner CD: Posterior cruciate ligament injuries in the adult. In DeLee JC, Drez D Jr, Miller MD [eds]: Orthopaedic Sports Medicine, 2nd ed. Philadelphia, WB Saunders, 2003, pp 2083-2106.)

Anterior cruciate ligament

Anterior meniscofemoral ligament (ligament of Humphry)

Posterior horn of lateral meniscus

Posterior meniscofemoral ligament (ligament of Wrisberg)

Posterior cruciate ligament quently involve isolated PCL tears, while some authors report that as many as 90% of emergency department trauma patients with PCL disruptions have combined ligamentous injuries. Typically, these are higher grade PCL disruptions and are associated with injury involving the PLCC structures.3,5

Regardless of the circumstances, the most common mechanism of injury involves a posteriorly directed force to the proximal tibia of a flexed knee (Fig. 53-5).This may occur in contact sports when a tackle causes a direct blow to the anterior tibia but also may occur when a player falls forward onto the knee, especially if the foot is in plantar flexion, which allows the

Figure 53-5 The most common mechanism of posterior cruciate ligament injury involves a direct force to the front of a flexed knee. (From Giffin JR, Annunziata CC, Harner CD: Posterior cruciate ligament injuries in the adult. In DeLee JC, Drez D Jr, Miller MD [eds]: Orthopaedic Sports Medicine, 2nd ed. Philadelphia, WB Saunders, 2003, pp 2083-2106.)

ground force vector to intersect the proximal tibia. When the foot is dorsiflexed, the ground force vector contacts the patella and distal femur, avoiding undue stress across the knee ligaments. In motor vehicle trauma, the classic mechanism involves a dashboard injury in which the knee and proximal tibia of a front seat rider strikes the dashboard.1 Forced hyperflexion with or without tibial load is a less common but well-reported mechanism of injury. Indirect methods of injury include twisting and hyperextension and often lead to combined ligament injuries.1,7 Significant varus or valgus force usually only disrupts the PCL after rupture of the appropriate collateral ligament.13

CLINICAL FEATURES AND EVALUATION

The first step in determining appropriate management is accurate diagnosis. Isolated PCL tears are commonly overlooked during the initial evaluation, as history is often vague and physical examination findings are subtle. Partial, or even complete, isolated tears usually present with relatively benign symptoms.1 A thorough history should be obtained with special emphasis on the mechanism of injury, as this may give important information regarding injury severity and possible associated injuries.

Unfortunately, awareness of ligamentous injury at the moment of PCL disruption is infrequent and many patients are unable to describe precisely how the injury occurred. Some patients may describe a "pop" or tearing sensation at the moment of injury but be unable to describe the exact biome-chanical forces that occurred. Location and timing of pain, sensation of instability, and performance-related impairment are important complaints to elicit. During the acute phase of injury, patients may complain of a mild or moderate effusion and posterior knee pain or pain with kneeling. Instability in isolated PCL injury is an infrequent complaint and should lead the physician to suspect associated injuries. In subacute or chronic PCL injury, complaints may include vague anterior knee pain or pain with deceleration or stair descent. Commonly in chronic injury, patients may describe dull, aching pain localized to the patellofemoral and medial compartments.5

On physical examination, observe the patient's gait and static weight-bearing alignment of the extremity. Varus thrust, where the knee shifts into varus during foot strike, is common in chronic posterolateral deficiency.1,2 In acute injury, the skin

Box 53-1 Clinical Diagnosis of Posterior Cruciate Ligament Injuries

Posterior drawer test

Posterior sag (Godfrey) test

Quadriceps active test

Dynamic posterior shift test

Reverse pivot-shift test

Dial (external rotation) test

Whipple test

should be observed for any signs of trauma, especially over proximal tibia, and bruising may be found in the popliteal fossa from posterior capsular rupture.

There are a number of specific maneuvers described to evaluate the PCL and its associated structures. Of these, the posterior drawer test is considered the most accurate (Box 53-1).

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