Posterior Cruciate Ligament Injury

The posterior cruciate ligament (PCL) is a strong fibrous tissue present inside the knee joint. The PCL along with the anterior cruciate ligament (ACL) plays an important role in the stabilization of the knee joint. The PCL may be injured while playing sports, accidental slipping, or a motor vehicle accident.

PCL injuries occur less often than the more common ACL injuries. While low-grade PCL injuries may be managed nonsurgically, high-grade injuries usually require surgical management.

Anatomy

The posterior cruciate ligament attaches the inner side of the lower thigh bone with the back of the upper shin bone. The cruciate ligaments are rope-like tough structures that stabilize the knee during day-to-day activities such as walking, turning, twisting, running, etc.

MRI showing the normal cruciate ligaments in the knee joint in the sagittal section.

The PCL ligament consists of two bundles, the anterolateral bundle, and the posteromedial bundle. While the anterolateral bundle is taut in a bent knee, the posteromedial bundle is taut in a straight knee.

The PCL primarily functions to prevent excessive movement of the shin bone against the thigh bone. The PCL also prevents excessive inner rotation of the leg in both flexion and extension. In a straight knee, PCL also functions to prevent excessive side-to-side movement of the knee.

The PCL is also responsible to prevent overshooting of the leg on straightening. As the PCL functions in conjunction with the ACL and the collateral ligaments, injury to the PCL often occurs in association with other knee ligament/meniscus injuries.

Injury

The PCL injury may occur in conjunction with other knee ligament injuries or may occur as an isolated injury. The injury mostly occurs as an acute injury following trauma but may also occur as a chronic injury secondary to repeated trauma.

The most common mechanism of PCL injury is falling with bent knees. As the shin bone is pushed against the thigh bone, the PCL ruptures/tears. The injury may also occur as a result of dashboard injury during a motor vehicle accident when the bent knee hits the dashboard which pushes the shin bone back against the thigh bone.

Other mechanisms of injury include traumatic knee dislocation, knee rotational injuries, etc. Athletes playing sports such as football, rugby, soccer, basketball, etc are especially vulnerable to PCL injuries.

Symptoms

The symptoms of PCL injuries as a result of acute injury present as acute pain, swelling, and difficulty walking. Patients may complain of laxity of the knee joint with a sensation of the knee giving away. Patients with isolated PCL injury may at times present with minimal symptoms. Similarly, patients with chronic PCL tears may present with only mild knee pain and instability.

Diagnosis

The physician elicits a detailed history surrounding the injury. The mechanism of injury may point towards the probable structure damaged in the knee. The physical examination involves special tests and maneuvers to test the integrity of various ligaments in the knee.

Commonly, the physician performs a posterior drawer test. The posterior drawer test involves the patient lying on the bed with their back towards the bed. The patient’s knee is bent at 90 degrees and the physician tests by trying to push the leg back against the thigh after first trying to pull the knee forward. The test is positive if there is excessive laxity on pushing the leg back.

The physician grades the PCL injury by the degree of laxity of the knee on performing the posterior drawer test. Similarly, the physician tests for the integrity of the other ligaments and meniscus in the knee.

An X-ray is usually requested to look for any bony injuries. Severe PCL injuries may result in an avulsion of a bony fragment along with the ligament which may be visible on an X-ray. The ligaments and other soft tissues are most clearly recognized on an MRI.

Intraoperative skin markings of the knee joint before arthroscopic reconstruction.

Management

Acute injuries with a bony avulsion may necessitate immediate surgery to fix and reconstruct the PCL ligament. Such injuries are usually associated with injuries to other structures of the knee. Grade 1 and 2 injuries are generally managed with nonsurgical techniques.

The physician may prescribe pain medication to help control pain. Icing is advised to help control the swelling. Icing and compression bandage helps to reduce swelling after acute injury. A knee brace is usually advised to help provide stability to the knee and help in healing.

Surgical reconstruction is done in case the conservative management fails to provide relief and in grade 3 and 4 injuries. The surgical reconstruction involves either the use of allograft or autograft. The allograft is harvested from a cadaver while an autograft is harvested from the patient’s own body.

The Achilles tendon, hamstrings tendon, or quadriceps tendon may be used as an autograft for PCL reconstruction. The reconstruction is usually done with the use of an arthroscope. In arthroscopic surgery, the surgeon uses keyhole incisions to insert miniature instruments along with a camera that projects the view on an outside display.

A rehabilitation program is started after the surgery to help the patient regain the strength and flexibility of the muscles surrounding the knee joint. The patients are able to get back to their day-to-day activities and sports after the rehabilitation period.