Which muscle is often involved in "runner's knee" (patellofemoral pain syndrome)?

The vastus lateralis muscle is a key component of the quadriceps muscle group, located on the lateral side of the thigh. It plays a crucial role in knee extension and in stabilizing the patella during movements. In the context of "runner's knee," also known as patellofemoral pain syndrome, the vastus lateralis can be involved due to its influence on patellar tracking. If the muscle is weak or imbalanced relative to other muscles, it can lead to improper alignment of the patella as the knee flexes and extends, resulting in pain and discomfort.

Runner's knee often arises from repetitive stress, muscle imbalances, and overuse, particularly in activities like running that involve significant knee movement. Strengthening the vastus lateralis, along with other components of the quadriceps, can help alleviate some of these symptoms by improving the stability and proper tracking of the patella within the femoral groove. This is why the vastus lateralis is often highlighted in relation to this condition.