Snapping popliteus tendon within an osteochondritis dissecans lesion: an unusual case of lateral knee pain.

The popliteus muscle is an important structure in the posterior knee, coursing from the distal lateral femoral condyle to the posterior tibia, and it initiates knee flexion, protects the lateral meniscus, and resists tibial external rotation. Abnormalities in the lateral femoral condyle may result in impaired tracking of the popliteus tendon over the lateral femoral condyle, causing pain and a snapping sensation. We report a case of a snapping popliteus tendon caused by an osteochondral defect of the lateral femoral condyle. We obtained a thorough medical history, performed a detailed physical examination, and performed diagnostic ultrasonography to accurately diagnose the condition. The patient underwent open popliteus tenotomy and tibial tenodesis with excellent results and full return to activity. Any abnormality of the lateral femoral condyle may predispose patients to snapping popliteus tendon and we believe early diagnosis utilizing ultrasonography imaging and surgical intervention may benefit these patients significantly.