PCL and MCL injuries affect two of the key ligaments that help keep the knee stable under load, change of direction and impact. These injuries can occur on their own, but they may also form part of a more complex ligament injury pattern, particularly after higher-energy trauma.
Treatment decisions depend on which ligament has been injured, the severity of the injury, the stability of the knee and whether other structures are involved.
While most people have heard of the anterior cruciate ligament (ACL), the other ligaments in the knee are less well-known.
The posterior cruciate ligament (PCL) sits deep inside the centre of the knee joint and stops the shin bone from moving too far backwards under the thigh bone. The PCL is larger and thicker than the ACL, so greater force is usually required to injure it.
The medial collateral ligament (MCL) runs along the inner side of the knee. Its job is to support the inside of the joint and resist force pushing the knee inwards.
MCL injuries typically occur when the knee is forced inwards into a valgus or “knock-knee” position. This may happen in contact sports, twisting injuries or awkward landings.
PCL injuries usually follow a direct blow to the front of a bent knee or a significant fall. They may happen when you land heavily on a bent knee, collide with another player or strike the dashboard in a car accident.
Sometimes, only the PCL or MCL is injured. Quite often, though, they occur alongside other injuries, such as the ACL, meniscus or a more complex multi-ligament pattern.
Both PCL and MCL injuries can cause pain and swelling and make you hesitant to trust your knee.
An MCL injury often causes tenderness along the inner side of the knee and a feeling that the joint is loose or sloppy early on. A PCL injury may be more subtle, but it can cause swelling, pain with weight-bearing, difficulty with stairs and a sense that the knee is not quite stable, especially under load. If the whole knee swells rapidly or feels markedly unstable, there may be more than one structure involved.
Diagnosis begins with a careful history, clinical examination and scans, such as:
Many isolated MCL and PCL injuries can be managed without surgery.
Bracing may be used to support healing, reduce the risk of the ligament stretching and, for PCL tears, to hold the tibia in the right position. The mainstay of non-surgical treatment is physiotherapy to help improve movement, strength and control.
In these cases, repair or reconstruction may be needed. Recovery depends on the severity and combination of injuries, but it is typically measured in months rather than weeks.
PCL and MCL injuries are not always straightforward and benefit from careful assessment in a knee-focused practice, where both operative and non-operative pathways can be considered.