Your kneecap (patella) sits over the front of your knee joint. As you bend or straighten your knee, the underside of your kneecap glides over a groove in the bones that make up your knee joint.
A kneecap can be knocked out of the groove when the knee is hit from the side.
A kneecap can also slide out of the groove during normal movement or when there is twisting motion or a sudden turn.
Kneecap subluxation or dislocation may occur more than once. The first few times it happens will be painful, and you will be unable to walk.
If subluxations continue to occur and are not treated, you may feel less pain when they happen, but these episodes can further damage your knee joint.
You may have had a knee x-ray or an MRI to make sure your kneecap bone did not break and there was no damage to the cartilage or tendons (other tissues in your knee joint).
If tests show that you do not have damage:
If your kneecap is damaged or unstable, you may need surgery to repair or stabilize it. Your health care provider will usually refer you to an orthopaedic surgeon.
Sit with your knee raised at least 4 times a day. This will help reduce swelling.
Ice your knee. Make an ice pack by putting ice cubes in a plastic bag and wrapping a cloth around it.
Pain medicines such as acetaminophen, ibuprofen (Advil, Motrin, and others), or naproxen (Aleve, Naprosyn, and others) may help ease pain and swelling.
You will need to change your activity while you are wearing a splint or brace. Your health care provider will advise you about:
Many exercises can help stretch and strengthen the muscles around your knee, thigh, and hip. Your health care provider may show these to you or may have you work with a physical therapist to learn them.
Before returning to sports or strenuous activity, your injured leg should be a strong as your uninjured leg. You should also be able to:
Call your health care provider if:
Patellar subluxation - aftercare; Patellofemoral subluxation - aftercare; Kneecap subluxation- aftercare
De Carlo M, Armstrong B. Rehabilitation of the knee following sports injury. Clin Sports Med. 2010;29:81-106.
Steiner T, Parker RD. Patella: subluxation and dislocation. 2. Patellofemoral instability: recurrent dislocation of the patella. In: DeLee JC, Drez D Jr., Miller MD, eds. DeLee and Drez's Orthopaedic Sports Medicine. 3rd ed. Philadelphia, Pa: Saunders Elsevier;2009:chap22;sect C.
Hing CB, Smith TO, Donell S, Song F. Surgical versus non-surgical interventions for treating patellar dislocation. Cochrane Database Syst Rev. 2011;11:CD008106.
Updated by: C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
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