What is a PCL Injury?
There are 4 ligaments in the knee that provide stability to the knee joint and aim to provide protection to the knee. When a force is applied to the knee that would cause a range of motion beyond motion that is considered normal in the leg, these protective ligaments become pulled taut and resist that force, preventing motion from going beyond normal. Sometimes, the ligaments lose this tug of war and the extreme force that was applied to the leg wins. It overcomes the resistance of the ligament and causes it to tear.
The Posterior Cruciate Ligament (PCL) is less well known than the Anterior Cruciate Ligament (ACL). These two ligaments are very similar in structure but opposite in the jobs that they perform. The word ‘cruciate’ means crossing. The PCL crosses perpendicular to the ACL in the knee and the two ligaments form the shape of a cross. The ACL attachments go from the back of the bottom of the femur to the front of the top of the tibia and its main job is to prevent hyperextension of the knee. The PCL, on the other hand, is the exact opposite. Its attachments run from the front of the bottom of the femur to the back of to the top of the tibia with the main job of this ligament being to prevent hyperflexion of the knee. There are four different grades of PCL tears that you may be diagnosed with:
- Grade I: minor tear to the PCL that does not significantly affect the ability of the PCL to provide stability
- Grade II: a partially torn PCL, the ligament is much looser and begins to affect stability
- Grade III: a complete tearing of the ligament where surgical intervention will most likely be needed
Symptoms of a PCL Injury
Symptoms of a strain or tear of the PCL can mimic those of other acute orthopedic injuries, but there are symptoms that will be unique to a PCL tear that you should be made aware of. As always, a prompt, accurate diagnosis is needed in order to definitively diagnose a PCL tear, usually through means of an MRI of the knee. Symptoms include:
- Severe pain, usually located in the back of the knee, causing posterior knee pain
- You may have heard a ‘popping’ sound at the time of injury
- Stiffness and loss of range of motion of the knee
- Swelling erythema (reddening of skin), and warmth
- Feelings of instability when you put weight on the affected leg or attempt to walk
PCL injuries are far less common than ACL injuries.
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What Causes a PCL Injury?
The function of the PCL is to both prevent tibia from moving too far posteriorly with respect to the femur. A common injury involving the PCL is called the “dashboard injury.” Think of when you are sitting in the passenger side of a car. You may have your knees bent and elevated with them resting on the dashboard. If the car that you are riding in suddenly stops, the tibia will be pushed backward as the rest of your body moves forcefully forward from the momentum of the car accident. This is why these injuries are sometimes called “dashboard injuries.” But, aside from dashboards in cars, there are other causes of a PCL strain or tear. These are:
- Direct blows to a flexed (bent) knee
- A hard fall directly on the knee
- High impact, contact sports
- Any other forceful motion that would force the tibia posterior (back) relative to the femur
How to Treat PCL Injury
There are various treatment strategies that your doctor will discuss with you. The method chosen in order to heal this area will depend on the severity of the injury, and how disabling it has been to your life.
The first line of dense is the same with most acute orthopedic injuries. This is the RICE Protocol which stands for
- Elevation: with elevation, you always want to elevate the injured area above heart level in order to encourage proper flow to and from the heart
Limiting physical activity until the pain and swelling have decreased substantially will be necessary. Walking with crutches for a while may be necessary in order to decrease the weight that is borne on the affected knee joint. A course of physical therapy will most likely be ordered in order to stretch and strengthen the surrounding musculature and use other modalities that aid in reducing pain and healing. In more severe cases, surgical intervention may be necessary.