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Patellar Instability
(Dislocating Kneecap)


The kneecap, patella, is a bone that connects the thigh and shinbone through tendon connections. The patella allows for the leg to straighten and bend.

Causes & Symptoms

Typically, the kneecap fits and slides smoothly in its groove. In some cases the groove is uneven or too shallow and the kneecap may partially or completely dislocate with motion. In the setting of a traumatic injury, a sharp blow to the kneecap may tear the ligaments that stabilize the kneecap and may cause the kneecap to dislocate.

Symptoms of a knee cap dislocation or patellar instability include buckling, repeat sensation of dislocation, catching with bending, stiffness, and swelling.

Evaluation & Treatment

Evaluation includes a detailed history and physical examination maneuvers.

Initial evaluation includes a detailed history, physical examination, and x-rays to evaluate the groove. Specialized examination maneuvers may be done to determine the extent of laxity. An MRI may be ordered to evaluate for ligament damage.

Initial treatment is based on the number of previous dislocation events. In those who are first time dislocators, nonsurgical treatment is indicated. Nonsurgical treatment focuses on utilizing a stabilizing brace, swelling reduction and strengthening of the hip and quadriceps muscles.

Surgical treatment is considered for those who have had multiple dislocations not improved with physical therapy and those with associated injuries such as cartilage damage. Surgical treatment is done through a small incision as an outpatient. Return to normal activities occurs between 1 to 3 months.