Overview

Patellofemoral (puh-tel-o-FEM-uh-rul) pain syndrome is pain at the front of your knee, around your kneecap (patella). Sometimes called "runner's knee," it's more common in people who participate in sports that involve running and jumping.

The knee pain often increases when you run, walk up or down stairs, sit for long periods, or squat. Simple treatments — such as rest and ice — often help, but sometimes physical therapy is needed to ease patellofemoral pain.

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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.

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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.

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Diagnosis

Your doctor will ask about your history of knee problems and will press on areas of your knee and move your leg into a variety of positions to help rule out other conditions that have similar signs and symptoms.

To help determine the cause of your knee pain, your doctor might recommend imaging tests such as:

• X-rays. A small amount of radiation passes through your body in the process of creating X-ray images. This technique visualizes bone well, but it is less effective at viewing soft tissues.
• CT scans. These combine X-ray images from various angles to create cross-sectional images of internal structures. CT scans can visualize both bone and soft tissues, but the procedure delivers a much higher dose of radiation than do plain X-rays.
• MRI. Using radio waves and a strong magnetic field, MRIs produce detailed images of bones and soft tissues, such as the knee ligaments and cartilage. But MRIs are much more expensive than X-rays or CT scans.

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Prevention

Sometimes knee pain just happens. But certain steps may help prevent the pain.

• Maintain strength. Strong quadriceps and hip abductor muscles help keep the knee balanced during activity, but avoid deep squatting during your weight training.
• Think alignment and technique. Ask your doctor or physical therapist about flexibility and strength exercises to optimize your technique for jumping, running and pivoting — and to help the patella track properly in its groove. Especially important is exercise for your outer hip muscles to prevent your knee from caving inward when you squat, land from a jump or step down from a step.
• Lose excess pounds. If you're overweight, losing weight relieves stress on your knees.
• Warm up. Before running or other exercise, warm up with five minutes or so of light activity.
• Stretch. Promote flexibility with gentle stretching exercises.
• Increase intensity gradually. Avoid sudden changes in the intensity of your workouts.
• Practice shoe smarts. Make sure your shoes fit well and provide good shock absorption. If you have flat feet, consider shoe inserts.

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.

Source: http://www.mayoclinic.com