The posterior cruciate ligament (PCL) is one of four ligaments that hold the knee in place and provide added stability. More specifically, the PCL helps to ensure proper alignment of the femur and tibia, also called the thighbone and shinbone. Ligaments are fibrous tissue that usually connect bones.

The PCL holds the shinbone in place so that it doesn’t slip over the thighbone and cause the knee to buckle, lock, or collapse. According to Medline Plus, the PCL is the strongest ligament in the knee. An injury to the posterior cruciate ligament may or may not require surgery, depending upon the severity of the injury, age of the patient, and whether other ligaments and cartilage are involved.

The PCL can be injured by landing on it awkwardly, falling hard on a bent knee, or receiving a direct blow to a flexed knee. The posterior cruciate ligament may be rehabilitated through physical therapy exercises designed to strengthen the leg muscles around the knee. In the worst cases, ligament replacement is the only way to completely repair a PCL injury.