Causes

Doctors aren't certain what causes patellofemoral pain syndrome, but it's been associated with:

• Overuse. Running or jumping sports puts repetitive stress on your knee joint, which can cause irritation under the kneecap.
• Muscle imbalances or weaknesses. Patellofemoral pain can occur when the muscles around your hip and knee don't keep your kneecap properly aligned. Inward movement of the knee during a squat has been found to be associated with patellofemoral pain.
• Injury. Trauma to the kneecap, such as a dislocation or fracture, has been linked to patellofemoral pain syndrome.
• Surgery. Knee surgery, particularly repair to the anterior cruciate ligament using your own patellar tendon as a graft, increases the risk of patellofemoral pain.