Symptoms and causes

Symptoms

Patellofemoral pain syndrome usually causes a dull, aching pain in the front of your knee. This pain can be aggravated when you:

  • Walk up or down stairs
  • Kneel or squat
  • Sit with a bent knee for long periods of time

When to see your doctor

If the knee pain doesn't improve within a few days, consult your doctor.

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.

Risk factors

Factors that can increase your risk include:

  • Age. Patellofemoral pain syndrome typically affects adolescents and young adults. Knee problems in older populations are more commonly caused by arthritis.
  • Sex. Women are twice as likely as men are to develop patellofemoral pain. This may be because a woman's wider pelvis increases the angle at which the bones in the knee joint meet.
  • Certain sports. Participation in running and jumping sports can put extra stress on your knees, especially when you increase your training level.