A posterior cruciate ligament (PCL) injury happens when the biomechanical limits of this major knee ligament are overextended. This injury may be the result of a blow to a bent knee, falling hard on a bent knee, or from an overextension the knee. An injury to the PCL can involve mild to severe ligament damage and is often associated with other knee injuries.
The knee joint is a complex hinge joint connecting the thighbone (femur), which is the longest bone in the body, to the second longest bone in the body, the shinbone (tibia). It is the largest joint in the body and acts in coordination with the pelvis, hip, upper leg, lower leg, ankle and foot to facilitate a complete range of lower body movements. The knee is a strong weight-bearing joint that allows the leg to flex, extend, and twist slightly from side to side.
There are four major ligaments in the knee. The two located at the sides of the knee are known as the collateral ligaments and the two crossing each other within the joint are the cruciate ligaments. These four ligaments, along with help from the quadriceps muscles in the front of the thighs and the hamstrings in the back of the thighs, act to stabilize the knee and keep it moving in the proper direction. The posterior cruciate ligament runs along the back of the knee joint from the bottom of the thighbone to the top of the shinbone. It helps to insure proper alignment of the knee and keeps the shinbone from moving too far backwards.
The posterior cruciate ligament is the strongest of the four major stabilizing ligaments in the knee and the least frequently injured. An injury to this ligament requires a powerful force. Consequently, the knee trauma that produces a PCL injury is often severe enough to damage other ligaments and associated structures within the knee.
The PCL become injured from a direct blow to the flexed knee. Smashing your knee in a car accident or falling hard on a bent knee in a sports activity are often sources of PCL damage. Hyperextension of the knee following an awkward landing from a jump may also injure the ligament.
Symptoms of a PCL injury may include:
- Pain and swelling
- Stiffness in the joint
- Tenderness in the knee (specifically the back of the knee)
- Instability in the knee joint
- Difficulty walking
Evaluating for PCL damage begins with a thorough history of the injury and the performance of a physical exam. During the clinical examination the doctor will check for pain and tenderness in the knee as well as assess the joint as the knee is moved in a variety of directions. Imaging tests may be ordered to evaluate the PCL in detail, to check for associated damage, and to rule out other disorders.
Treatment depends on the extent of the injury. For minor injuries the ligament may heal without complications. Non-surgical treatment following the injury may include RICE (rest, ice, compression, and elevation), a period of immobilization with a brace and possibly crutches, as well as physical therapy. If the symptoms are not alleviated with conservative treatment, if the damage is significant or if there are combined injuries in the knee, then surgery may be recommended. With surgery the torn posterior cruciate ligament can be rebuilt. Recovery time from a surgical procedure depends on the severity of the injury. Combined injuries take a longer time to heal. Physical therapy is an essential part of rehabilitation.