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Patellar Dislocation and Instability

What is patellar dislocation and instability?

The kneecap, or patella, runs in a groove (the trochlea) along the front of the knee. It is kept in place by the bony contours of this groove, as well as ligaments (soft tissue bands) that keep the patella from moving side to side. The kneecap can be forced out of its groove during a knee injury, causing the knee to become dislocated. Usually the kneecap slips back into place, but occasionally it does not and requires a trip to the emergency room to have it put back in place. In less severe cases, the kneecap can slip partially out of place and then quickly re-center itself (called a patellar subluxation).

What are the symptoms of patellar dislocation and instability?

There is often intense pain and swelling associated with a kneecap dislocation. Initially it may be difficult to stand or walk, resulting in the need for crutches during the early stages. If the instability becomes chronic, the kneecap may frequently slide (partially or completely) out of place. These episodes can become less painful but more frequent over time.

How are patellar dislocation and instability diagnosed?

Diagnosis is generally made through a discussion with your doctor and a thorough examination. Your sports medicine specialist will check how the kneecap runs in its groove, test how stable it is and look at the alignment of the kneecap. X-rays are used to look at the shape and structure of the kneecap and groove. An MRI is often used to look at the surface of the kneecap, as well as the kneecap ligaments.

How are patellar dislocation and instability treated?

After a kneecap dislocation, the individual may be placed in an immobilizer brace for a period of time to allow the patella to rest and heal. The good news is that most people who rehab appropriately after a first kneecap dislocation tend to not have recurrent problems. In the less common case of repetitive patellar dislocations, surgery can be done to stabilize the patella and prevent it from sliding out.

Sports Medicine Appointments & Referrals


Sports Medicine Locations

UC San Diego Health offers expertise in sports medicine within family medicine, orthopedics, surgery and rehab. Not all services are available at all locations.

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Scripps Ranch