Practice Essentials
The posterior cruciate ligament (PCL) courses from the posterior intercondylar area of the tibia to the medial condyle of the femur. It gives dynamic stability to the knee by preventing posterior displacement of the tibia on the femur. The PCL is an extrasynovial structure composed of a large anterolateral portion and a small posteromedial portion. [1]
The PCL resists 85-100% of posteriorly directed forces at 30º and 90º of knee flexion. The 2 bands of the PCL, the anterolateral band and the posteromedial band, have different tension patterns. The anterolateral band is under great tension during knee flexion, whereas the posteromedial band is under more tension during knee extension.
Signs and symptoms of posterior cruciate ligament injury
Pain and limited range of motion (ROM) after an injury are the most common symptoms of posterior cruciate ligament (PCL) trauma with associated ligamentous injuries.
The posterior drawer test performed with the knee at 90° is the most sensitive test for detecting PCL injury. The change in the step off from 1 cm (normal) from the medial tibial plateau anterior to the medial femoral condyle is absent, as compared with the healthy knee. This test is 90% sensitive and 99% specific in the diagnosis of PCL injury. [2]
Adjuvant tests can increase the sensitivity for diagnosis of PCL injuries. These include the following:
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Quadriceps active test - If the PCL is injured or absent, the tibia translates anteriorly from a subluxated position
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Dynamic posterior shift test - A positive result occurs when the tibia reduces with a click near full extension
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Posteromedial and posterolateral instability test
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Posterolateral drawer test
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Reverse pivot shift test - If the posteriorly subluxated tibial plateau abruptly shifts back to the reduced position, the result is positive
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Godfrey, or posterior sag, test - Posterior tibial translation is an indication of an injured or insufficient PCL
Workup in posterior cruciate ligament injury
Laboratory studies include the following:
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Complete blood cell (CBC)
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C-reactive protein (CRP)
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Comprehensive metabolic panel (CMP)
Other tests include the following:
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Magnetic resonance imaging (MRI) - Found to be 80% sensitive and 97% specific in the diagnosis of complete PCL tears
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Diagnostic arthroscopy – Allows direct visualization of the PCL
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Knee aspiration – Should be conducted if effusion is present, to rule out causes of effusion other than PCL injury
Management of posterior cruciate ligament injury
Physical therapy
A grade I or grade II injury is usually treated with a brief period of knee splinting in extension, followed by early ROM therapy and a quadriceps-and-hamstring–strengthening program (that is particularly eccentric). [3, 4, 5, 6, 7] Recovery is quick, and many patients are able to return to normal function in about 4 weeks. Closed and open kinetic chain exercises are recommended.
The postoperative protocol includes the use of a knee brace in extension, with weight bearing as tolerated for 4 weeks, as well as the use of quadriceps-strengthening exercises. Later, closed chain exercises are performed at 6 weeks, and proprioceptive training is carried out at 12 weeks. Hamstring exercises are delayed for 4 months to decrease the posterior load on the tibia. Patients can begin light jogging at 6 months. Cycling and aerobic exercise can also benefit the patient and can help to restore function. [8, 9, 10]
Surgical therapy
Grade III PCL injuries may need surgical intervention. Tibial avulsion fractures with a PCL injury also require such intervention. [3, 11]
Suture repair of insertion site avulsions is effective if it is performed less than 3 weeks after the injury. Nonabsorbable sutures are placed through the avulsed ligament and tied over the bone bridge. Unfortunately, the results are often unsatisfactory.
Other surgical techniques can rely on a single or a double reconstruction procedure. [12]
Related Medscape Drugs & Diseases topics:
MRI for Posterior Cruciate Ligament Injuries
Posterior Cruciate Ligament Injury [Sports Medicine]
Posterior Cruciate Ligament Pathology
Related Medscape resource:
Resource Center Joint Disorders
Pathophysiology
Posterior cruciate ligament (PCL) injuries are usually the result of a direct blow to the anterior part of the tibia, with a hyperextension moment at the knee. Biomechanical studies have shown an increase in PCL force with knee flexion and the application of internal tibial torque, while other studies have shown that PCL-deficient knees have greater external tibial rotation. Several mechanisms have been implicated in PCL injury, including the following [13] :
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Posterior translation of the proximal tibia
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Dashboard injuries in motor vehicle accidents (the most common mechanisms)
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Falling on a flexed knee (the most common injury in sports, particularly in wrestling and football)
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Forced hyperflexion of the knee joint
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A posterior force applied against a hyperextended knee with the foot fixed
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Forced hyperextension of the knee
Epidemiology
Frequency
United States
There is a variable incidence of posterior cruciate ligament (PCL) injuries in the US population. In a retrospective study by Schulz and colleagues, 33% of the injuries were sports related. [13] As many as 20% of all knee ligament injuries consisted of PCL trauma.
International
International data about posterior cruciate ligament (PCL) injuries are limited. In Germany, approximately 8-10% of all severe ligament injuries involve the PCL, which means that annually, 4000-5000 members of the German population suffer a PCL rupture.
Mortality/Morbidity
Chronic posterior cruciate ligament (PCL) deficiency can cause or predispose individuals to these pathologies: (1) medial compartment osteoarthritis of the knee, (2) increased risk for meniscal injury, and (3) patellofemoral osteoarthritis. [14]
Age
In Schulz's study, the mean age at which posterior cruciate ligament (PCL) injury occurred was 27.5 years ± 9.9 years. [13]
