Posterior cruciate ligament (PCL), one of four major ligaments of the knee, is situated at the back of the knee. It connects the thighbone (femur) to the shinbone (tibia). The PCL limits the backward movement of the shinbone.
PCL injuries are very rare and difficult to detect when compared to other knee ligament injuries.
The posterior cruciate ligament is usually injured by a direct impact, such as a motor vehicle accident when the knee forcefully strikes against the dashboard or during sports participation when a twisting injury or overextension of the knee can also cause PCL injury.
Injuries to the PCL are graded based on the severity of injury.
- In grade I the ligament is mildly damaged and slightly stretched, but the knee joint is stable.
- In grade II there is a partial tear of the ligament.
- In grade III there is a complete tear of the ligament and the ligament is divided into two halves making the knee joint unstable.
Patients with PCL injuries usually experience knee pain and swelling immediately after the injury. This may also be associated with instability of the knee joint and knee stiffness that causes limping and difficulty walking.
Diagnosis of a PCL injury is made on the basis of symptoms, medical history, and physical examination of the knee. The doctor may order a few diagnostic tests such as X-rays and MRI scans. X-rays are useful to rule out avulsion fractures where the PCL tears off a piece of bone with it. An MRI scan is done for better visualization of the soft tissues.
Generally, surgery is considered in patients with a dislocated knee and multiple ligament injuries, including the PCL. Surgery involves reconstruction of the torn ligament using a tissue graft taken from another part of the body, or from a donor.
Surgery is usually carried out with the help of an arthroscope using a few small incisions. The basic steps involved in PCL reconstruction are as follows:
- The surgeon inspects the knee and removes any remains of the native PCL, using an arthroscopic shaver. Care is taken to preserve the ligament of Wrisberg if it is intact.
- The donor tendon is harvested from the patellar tendon or the semitendinosus and gracilis tendon.
- The soft tissue around the femur is debrided to assist the insertion of the graft.
- The tibial attachment site is also prepared by identifying the normal attachment of the PCL at the bottom of the PCL facet.
- For placing the graft, a tibial tunnel is created to the anatomic insertion of the PCL on the tibia.
- The sharp edges and soft tissues around the exit site of the tunnel are smoothed, with a rasp.
- The tendon allograft is inserted in the tunnel and fixed with a cannulated interference screw.
- The graft is made taut distally by removing any slack in the graft.
- The graft is then fixed to the tibia, with the help of staples.
- After fixation, normal posterior stability of the knee is assessed by employing the posterior drawer test.
- The incision is closed with sutures and covered with sterile dressings.
Patients are advised to maintain the knee in full extension, supported by a knee brace, for a period of 2 to 4 weeks. Patients should not bear any weight on the operated knee. Pillows or other supports are placed under the tibia, for the first two months after surgery, to prevent any posterior subluxation of the tibia.
Weight-bearing and rehabilitation is initiated after 8 weeks. Crutches are often required until you regain your normal strength.
Risks and Complications
Knee stiffness and residual instability are the most common complications associated with PCL reconstruction. The other possible complications include:
- Blood clots(Deep vein thrombosis)
- Nerve and blood vessel damage
- Failure of the graft
- Loosening of the graft
- Decreased range of motion
Posterior cruciate ligament (PCL) reconstruction is a surgical procedure which involves reconstructing the torn PCL ligament using a tissue graft which is taken from another part of our body or a deceased donor for treating PCL injuries that cause pain and swelling in the knee joint. Such injuries can also result in instability in the knee joint, knee stiffness that causes limping, and difficulty in walking.