Snapping popliteus tendon syndrome. A cause of mechanical knee popping in athletes.

Six patients with snapping in the knee were evaluated with clinical history, examination, radiographs, and other imaging. All patients were younger than 40 years and none had an arthritic process. Onset was traumatic in three patients, spontaneous in two, and post-surgical in one. The popping was on the direct lateral aspect of the knee. A consistent examination finding was that the popping was more prominent when the knee was loaded with varus stress during passive flexion and extension cycling, and that it was easily palpated midway between the lateral epicondyle and lateral joint line. Four patients were treated nonoperatively and two had operations. Of those treated without surgery, two had spontaneous resolution of the popping, in one the popping persisted, although not symptomatic enough to require surgery, and one had surgery later. In the surgical group, one patient was treated with popliteus tendon release and one with tenodesis of the popliteus tendon to the fibular collateral ligament. Both procedures were curative and neither led to complicating problems. Follow-up information was not available for the patient with late surgery. Snapping of the popliteus tendon should be recognized as a cause of lateral popping in the knee. It is easily confused with more common sources of mechanical symptoms. Awareness will allow accurate diagnosis and treatment, avoiding unnecessary diagnostic arthroscopy.