Your kneecap (patella) sits over the front of your knee joint. As you bend or straighten your knee, the underside of the patella glides over the bones that make up the knee.

Strong tendons help attach the kneecap to the bones and muscles that surround the knee. These tendons are called:

• The patellar tendon (where the kneecap attaches to the shin bone)
• The quadriceps tendon (where the thigh muscles attach to the top of the kneecap)

Anterior knee pain may occur when the kneecap does not move properly and rubs against the lower part of the thigh bone. This may occur because:

• The kneecap is in an abnormal position (also called poor alignment of the patellofemoral joint).
• There is tightness or weakness of the muscles on the front and back of your thigh.
• You are doing too much activity that places extra stress on the kneecap (such as running, jumping or twisting, skiing, or playing soccer).
• Your muscles are not balanced and your core muscles maybe weaker.
• The groove in the thighbone where the kneecap normally rests is too shallow.
• You have flat feet.
• Your lower leg alignment is abnormal.
• Your core stability is weak and causes knee malalignment.
• Excess body weight or over activity increases the stress on your kneecap.

Anterior knee pain is more common in:

• People who are overweight
• People who have had a dislocation, fracture, or other injury to the kneecap
• Runners, jumpers, skiers, bicyclists, and soccer players who exercise often
• Teenagers and healthy young adults, more often girls

Other possible causes of anterior knee pain include:

• Arthritis
• Pinching of the inner lining of the knee during movement (called synovial impingement or plica syndrome)

Anterior knee pain is a dull, aching pain that is most often felt in one or more location:

• Behind the kneecap (patella)
• Below the kneecap
• On the sides of the kneecap

One common symptom is a grating or grinding feeling when the knee is flexed (when the ankle is brought closer to the back of the thigh).

Symptoms may be more noticeable with:

• Deep knee bends
• Going down stairs
• Running downhill
• Standing up from a squatting position or after sitting for a while

Your health care provider will perform a physical exam. The knee may be tender and mildly swollen. Also, the kneecap may not be perfectly lined up with the thigh bone (femur).

When you flex your knee, you may feel a grinding feeling below the kneecap. Pressing the kneecap when the knee is straightening out may be painful.

Your provider may want you to do a single leg squat to look at muscle imbalance and your core stability.

X-rays are very often normal. However, a special x-ray view of the kneecap may show signs of arthritis or tilting.

MRI scans are rarely needed.

Resting the knee for a short period of time and taking nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen, or aspirin may help relieve pain.

Other things you can do to relieve anterior knee pain include:

• Change the way you exercise.
• Learn exercises to both strengthen and stretch the quadriceps and hamstring muscles.
• Learn exercises to strengthen your core.
• Lose weight (if you are overweight).
• Use special shoe inserts and support devices (orthotics) if you have flat feet.
• Tape your knee to realign the kneecap.
• Wear the correct running or sports shoes.
• Taping of your kneecap to improve tracking.

Rarely, surgery for pain behind the kneecap is needed. During the surgery:

• Kneecap cartilage that has been damaged may be removed.
• Changes may be made to the tendons to help the kneecap move more evenly.
• Kneecap may be realigned to allow for better joint movement.

Anterior knee pain often improves with a change in activity, exercise therapy, and the use of NSAIDs. Surgery is rarely needed. However, if your knee has symptoms like instability or swelling, then you should see your provider earlier.

Contact your provider if you have symptoms of this disorder.

Patellofemoral syndrome; Chondromalacia patella; Runner's knee; Patellar tendinitis; Jumper's knee

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Updated by: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.