Kneecap (Patellar) Subluxation

What is kneecap subluxation?

A subluxing patella (kneecap) is a temporary, partial dislocation of the kneecap from its normal position in the groove in the end of the thigh bone (femur). This groove is located between two bumps at the end of the thigh bone called the femoral condyles.

What is the cause?

This temporary dislocation of the kneecap usually happens during forced leg straightening, with the kneecap moving out of the groove to the outer side of the knee.

The cause is usually abnormal structure in the leg. The inner thigh muscle may be underdeveloped or the outer thigh muscle may be overdeveloped. Your kneecap may be higher in the leg than most people’s kneecaps. You may be knock-kneed or the outer side of the femur bone may be underdeveloped.

What are the symptoms?

You may feel the kneecap moving out of position. You may have swelling and pain behind the kneecap. You may have pain when you bend or straighten your leg.

How is it diagnosed?

Your healthcare provider will ask about your symptoms and examine your knee. He or she may be able to feel the kneecap slipping to the outside as you bend and straighten your leg. An X-ray may show underdevelopment of the lateral femoral condyle.

How is it treated?

To treat this condition:

  • Put an ice pack, gel pack, or package of frozen vegetables wrapped in a cloth on your knee every 3 to 4 hours for up to 20 minutes at a time until the pain goes away.
  • Raise the knee on a pillow when you sit or lie down.
  • Take an anti-inflammatory medicine, such as ibuprofen, as directed by your provider. Nonsteroidal anti-inflammatory medicines (NSAIDs) may cause stomach bleeding and other problems. These risks increase with age. Read the label and take as directed. Unless recommended by your healthcare provider, do not take for more than 10 days.
  • Wear a brace prescribed by your healthcare provider to keep your kneecap in place.
  • Follow your provider’s instructions for doing exercises to help you recover.

Some people need surgery to keep the kneecap from subluxing.

While you are recovering from your injury you will need to change your sport or activity to one that will not make your condition worse. For example, you may need to bicycle instead of run.

Follow your healthcare provider's instructions. Ask your provider:

  • How and when you will hear your test results
  • How long it will take to recover
  • What activities you should avoid and when you can return to your normal activities
  • How to take care of yourself at home
  • What symptoms or problems you should watch for and what to do if you have them

Make sure you know when you should come back for a checkup.

How can I help prevent a subluxing kneecap?

A subluxing kneecap is best prevented by keeping your thigh muscles strong, especially the group of muscles on the inner side of the thigh.

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Published by RelayHealth.
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