The posterolateral corner (PLC) of the knee designates a group of ligaments and muscles along the back and outside edge of the knee joint. These include the lateral head of the gastrocnemius (calf) muscle, the popliteus (muscle), and three specific ligaments.
Damage to this corner of the joint is rare but can occur with traumatic injury from a sports-related accident, car accident, or fall. An isolated injury to the posterolateral corner can occur. But usually it’s linked with trauma to some other part of the knee — most often the meniscus or the cruciate ligaments that criss-cross inside the knee.
A person with a weak posterolateral corner will experience hyperextension of the knee when walking or going up and down stairs. Hyperextension means the knee goes back past a straight (extended) position because the mechanism that holds it in neutral is torn or damaged in some way. Every time you take a step, the knee pushes back farther than it should. The natural response to this awkward problem is to walk with the knee slightly bent and t avoid full extension.
Walking with the knee bent is a functional solution (it works), but it’s not a very good long-term solution. You can try a rehab program to strengthen the muscles around the knee. Surgery may be needed to fix the problem. Without surgery, an unstable knee joint remains at risk for further injuries (and subsequent damage). Early joint degeneration and subsequent osteoarthritis may develop as a result of the uneven forces and load placed on the joint.
Your surgeon can give you a better idea of what to expect based on the extent of damage present and the condition of the surrounding soft tissues. Your own personal goals for level of activity (e.g., exercise, sports or other recreational activities) can make a difference, too.