Recognizing and correctly diagnosing popliteus tendinitis is important because this condition can be painful, may significantly limit athletic performance, and can lead to unnecessary surgery if misdiagnosed. The diagnosis is largely established with a careful history and physical examination. Usually patients have symptoms that include tenderness along the course of the proximal popliteus tendon and pain with resisted external rotation. Treatment is directed at eccentric strengthening of the quadriceps to reduce strain on the popliteus. Most patients respond well to physical therapy and NSAIDs; however, recalcitrant cases may require local corticosteroid injection.