Posterior Cruciate Ligament Injury
The Posterior Cruciate Ligament (PCL) is one of the four ligaments located inside the capsule of the knee joint that hold the upper and lower leg bones together and stabilise the movement of the joint in certain directions.
The PCL, along with its counterpart, forms a cross (X) in the middle of the knee joint, hence named it is called “cruciate”. It stretches from the thigh-bone (femur) to the back of the joint surface of the lower leg bone (tibia). As it attaches posteriorly on the tibia, therefore, it is named the posterior cruciate ligament. It serves to restrict excessive backward movement of the tibia in relation to the femur.
The PCL is thicker and stronger than the Anterior Cruciate Ligament and for this reason suffers trauma less often. Moreover, PCL injury causes less pain and disability compared to that caused by ACL tearing. Despite that, it may require several months to heal completely. Contrary to ACL injuries, PCL injuries are more common in males.
Mechanism of Injury:
The typical mechanism by which one can injure the posterior cruciate ligament is by hitting a bent knee on a hard surface. This may happen during a motor vehicle accident or while playing soccer, football or any other contact sport.In an accident, a PCL injury occurs when a person hits a bent knee forcefully against the dashboard; also referred to as a “dashboard injury”. The part of the shin-bone just below the knee suffers a strong backwards jerk, resulting in PCL tearing.
In an accident, a PCL injury occurs when a person hits a bent knee forcefully against the dashboard; also referred to as a “dashboard injury”. The part of the shin-bone just below the knee suffers a strong backwards jerk, resulting in PCL tearing.
During sports, a player may hurt his PCL by falling hard on a bent knee, with his toes pointing down.
Mechanism of PCL injury
An isolated PCL injury can occur by bending the knee too far backwards, exceeding the normal limit.
- Mild to moderate pain, more if adjacent joint structures are also damaged.
- Pain intensifies on bending the knee such as while squatting or climbing stairs.
- Swelling appears soon after the injury, may be mild
- Joint instability, the knee feels wobbly on weight bearing.
- Bruising on the lower side of the knee
- Symptoms may worsen with time.
A PCL injury usually does not affect knee movement significantly. The history of trauma is suggestive of the diagnosis. However, certain orthopedic exams, as well as imaging techniques, are employed to confirm the diagnosis.
Posterior Tibial Sag:
The patient lays supine on the table with the knee bent at 90°. The knee end of the tibia sags a little backwards, demonstrating a deficient action of the PCL, which is responsible for limiting backward movement of the tibia relative to the femur.
MRI is an excellent diagnostic aid for detecting soft tissue injuries. It not only shows a PCL tear, if it is present; but it also helps to locate the extent of damage to the adjacent joint structures.
Arthroscopy is another technique employed for diagnosing PCL injury. As the name indicates, it involves viewing the joint through a tiny camera, inserted through a small cut.
X-rays help to locate any broken bone fragments, as sometimes the ligament may get detached from the bone together with a small bone chip.
A PCL injury usually consists of partial tearing of the ligament, which usually heals well on its own. Isolated PCL tears require only conservative therapy. Aggressive injuries involving tearing of multiple ligaments require surgical intervention for complete healing.
Immediately after the injury, it is advisable to:
Apply ice packs at the site of injury.
Support the injured joint and do not place any weight on the affected leg, slight compression is helpful.
Elevate the affected leg, to reduce bleeding or swelling.
A conservative approach involves immobilising the joint for a specific period using knee braces. Crutches may also be advised to further relieve pressure on the joint.
Once the initial symptoms subside, physiotherapy may commence. This consists of specific exercises that help to improve the range of knee movement.
Quadriceps and hip strengthening exercises help to improve joint stability. The quadriceps is a muscle group present on the front of the thigh and acts to straighten the leg. A well-conditioned quadriceps takes over the function of the PCL and prevents excessive backward displacement of the shin-bone relative to the thigh-bone.
Action of the quadriceps to restore PCL function
If the conservative approach fails to achieve joint stability, or if the injury is extensive involving other torn ligaments or damage to the joint cartilage, bone fracture, etc., surgery is required.
A torn PCL is usually reconstructed using a graft taken from another nearby ligament such as the hamstrings or from a donor body.
Arthroscopy is a less invasive surgical approach for diagnosing and treating damaged joints. A tiny camera, an arthroscope, is inserted through a small skin incision into the joint space. It allows the surgeon to visualise the operating field, as well as to repair the damaged ligament in certain instances. The advantages of arthroscopy include less post-operative discomfort and rapid recovery.
Possible complications include chronic joint pain and instability, as well as an increased risk of developing osteoarthritis.