Posterior cruciate ligament

Introduction

The posterior cruciate ligament (PCL) is one of the four major ligaments of the knee, connecting the posterior intercondylar area of the tibia to the medial condyle of the femur. This configuration allows the PCL to resist forces pushing the tibia posteriorly relative to the femur.

The PCL is an intracapsular ligament along with the anterior cruciate ligament (ACL) because it lies deep within the knee joint. Both are isolated from the fluid-filled synovial cavity, with the synovial membrane wrapped around them. The PCL gets its name by attaching to the posterior portion of the tibia.

Attachments

The posterior cruciate ligament is an intra-articular ligament in the knee that originates on the anterolateral border of the medial femoral condyle, at the point where the roof and intercondylar notch meet. It inserts 1-1.5 cm inferior to the posterior rim of the tibia, in the PCL fovea. This insertion is extra-artiular.

Course

The blood supply to the PCL is the middle genicular artery and it is innervated by the tibial nerve. The PCL’s average length is 38 mm and average width is 18 mm. It is made up of a anterolateral and posteromedial bundle, which are tight in flexion and extension, respectively. The tension in each bundle develops in a reciprocal fashion.

Function

The PCL acts as the primary restraint to posterior translation of the tibia and as the secondary restraint to external rotation. It has been found to resist 90% of the posterior force at 30 and 90 degrees of flexion. Other secondary restraints of the knee are the LCL, MCL and Posterolateral corner, all of which play a vital role in the PCL deficient knee. The posterolateral corner, PLC, is made up of the iliotibial band, LCL, biceps tendon, popliteus tendon and the popliteofibular ligament.

Disability if injured

• Pain, swelling, and decreased motion, causing an abnormal gait
• Instability; feeling like the knee may “give out”

Diagnosis of injury

• Posterior drawer test
• Posterior sag test

Treatment

Treatment is controversial. Grade I and Grade II tears are usually treated non-operatively (no weight-bearing, splinting, ice, elevation, physical therapy), while Grade III tears are generally reconstructed surgically a few weeks after the injury. Ligament reconstruction is used to replace the torn PCL with a new ligament, which is usually a graft taken from the hamstring or Achilles tendon from a host cadaver. An arthroscope allows a complete evaluation of the entire knee joint, including the patella, the cartilage surfaces, the meniscus, the ligaments (ACL and PCL), and the joint lining. The new ligament is then attached to femur and tibia with screws to hold it in place.