Posterior Cruciate Ligament Injuries
Injury to the posterior cruciate ligament (PCL) is less common than the nearby anterior cruciate ligament, comprising 5-20% of all knee ligament injuries. The average age of individuals sustaining acute PCL injuries ranges between 20-30 years. Injuries to the PCL can occur isolated, as well as in combination with other ligamentous or meniscal injuries.
Anatomy and Pathophysiology
The PCL has two bundles (anterolateral and posteromedial) and receives blood supply from the branches of the middle geniculate artery and fat pad. The PCL extends from the posterior tibial sulcus to the anterolateral medial femoral condyle.
This ligament provides a restraint to posterior tibial displacement, and injury often occurs during a direct blow to the proximal tibia when the knee if bent/flexed (a “dashboard injury”). PCL injuries may occur in combination with ligamentous and/or meniscal pathology.
PCL Injury Grades
- Grade I: partial tear, 1 to 5 mm of posterior tibial translation
- Grade II: complete tear, 6 to 10 mm of posterior tibial translation
- Grade III: complete tear combined with an associated injury (such as the posterolateral corner)
Physical Examination and Work-up
On examination, pain may be present posteriorly. A knee effusion or ecchymosis may be present. Both ROM and knee stability are assessed, including determining the grade of injury.
Posterior Drawer Test:
This clinical test is used to assess the integrity of the PCL. With the knee flexed to 90 degrees and the foot stabilized, the tibia is translated back posteriorly. The tibia will translate posteriorly in relation to the femur in the setting of a PCL tear.
Radiology
In the setting of laxity on exam, additional “stress X-rays” may be performed. Kneeling posterior stress radiographs reveal the difference between posterior translation in both knees and are particularly useful in the setting of a chronic PCL tear. Additionally, on X-ray, an avulsion fracture may be present. MRI is the modality of choice to characterize extent of injury and the presence of concurrent injuries of the knee.
Management of PCL Injuries
In the setting of Grade I and II injuries, nonoperative care of bracing rest and physical therapy are often successful. Physical therapy focuses on a knee extensor quadriceps strengthening program, with progression to co-contraction and hamstrings strengthening.
In the case of PCL avulsion fractures, primary repair of the bony avulsion via open reduction internal fixation may be considered. Grade III or combined ligamentous injuries may necessitate reconstruction of the affected ligaments with autograft or allograft. Post-operative rehabilitation is closely monitored and guided with criterion-based advancement based on regular exercise testing intervals at the COSMO Fit Lab.
