STUDY DESIGN: Case report. BACKGROUND: Determining the cause of painful snapping on the lateral aspect of the knee can be a challenge. The differential diagnosis includes iliotibial band friction syndrome, lateral meniscus tear, intra-articular loose body, discoid lateral meniscus, snapping biceps femoris tendon, degenerative joint disease, proximal tibiofibular joint instability, and snapping popliteus tendon. CASE DESCRIPTION: A 21-year-old female presented with a 7-year history of a painful snapping on the lateral aspect of her left knee. She reported the snapping occurred with all activities involving knee flexion and extension, including running and walking. With a diagnosis of snapping iliotibial band, she had received a variety of physical therapy interventions, including various lower extremity stretching and strengthening exercises. Nonsteroidal anti-inflammatory medications were also prescribed by her physician. Conservative and pharmoclogical interventions were unsuccessful in improving her symptoms. Similarly, our attempt with conservative treatment consisting of ice, taping, and a short period of immobilization was not successful. OUTCOMES: The patient underwent a surgical procedure consisting of removal of a prominent tubercle on the lateral femoral condyle and tenodesis of the popliteus tendon to the proximal aspect of the fibular (lateral) collateral ligament, followed by a postoperative program of physical therapy including range-of-motion and progressive strengthening exercises. At 6 weeks following surgery, the patient had returned to all activities with complete resolution of her symptoms. DISCUSSION: Painful snapping at the lateral aspect of the knee may be caused by a variety of disorders, including the popliteus tendon. Clinical diagnosis is challenging. Clinical suspicion of a snapping popliteus tendon as a source of the signs and symptoms of the condition is important for inclusion in the differential diagnosis. LEVEL OF EVIDENCE: Differential diagnosis, level 4.

J Orthop Sports Phys Ther. 2008;38(4):191-195, published online 14 December 2007. doi:10.2519/jospt.2008.2698