Posterior cruciate ligament (PCL) injury happens far less often than does injury to the knee's more vulnerable counterpart, the anterior cruciate ligament (ACL). The posterior cruciate ligament and ACL connect your thighbone (femur) to your shinbone (tibia). If either ligament is torn, it might cause pain, swelling and a feeling of instability.
Ligaments are strong bands of tissue that attach one bone to another. The cruciate (KROO-she-ate) ligaments connect the thighbone (femur) to the shinbone (tibia). The anterior and posterior cruciate ligaments form an "X" in the center of the knee.
Although a posterior cruciate ligament injury generally causes less pain, disability and knee instability than does an ACL tear, it can still sideline you for several weeks or months.
Signs and symptoms of a PCL injury can include:
- Pain. Mild to moderate pain in the knee can cause a slight limp or difficulty walking.
- Swelling. Knee swelling occurs rapidly, within hours of the injury.
- Instability. Your knee might feel loose, as if it's going to give way.
If there are no associated injuries to other parts of your knee, the signs and symptoms of a posterior cruciate ligament injury can be so mild that you might not notice that anything's wrong. Over time, the pain might worsen and your knee might feel more unstable. If other parts of your knee have also been injured, your signs and symptoms will likely be more severe.
The posterior cruciate ligament can tear if your shinbone is hit hard just below the knee or if you fall on a bent knee. These injuries are most common during:
- Motor vehicle accidents. A "dashboard injury" occurs when the driver's or passenger's bent knee slams against the dashboard, pushing in the shinbone just below the knee and causing the posterior cruciate ligament to tear.
- Contact sports. Athletes in sports such as football and soccer can tear their posterior cruciate ligament when they fall on a bent knee with their foot pointed down. The shinbone hits the ground first and it moves backward. Being tackled when your knee is bent also can cause this injury.
Being in a motor vehicle accident and participating in sports such as football and soccer are the most common risk factors for a PCL injury.
In many cases, other structures within the knee — including other ligaments or cartilage — also are damaged when you injure your posterior cruciate ligament. Depending on how many of these structures are damaged, you might have some long-term knee pain and instability. You might also be at higher risk of eventually developing arthritis in your affected knee.