Elbow instability Valgus instability of the elbow 2025-11-19T09:34:39Z A type of elbow instability that arises through injuries to the medial collateral ligament (MCL), specifically the anterior bundle (AMCL). In the valgus stress test, the elbow is placed in 20 to 30 degrees of flexion with the forearm supinated and a valgus stress is applied. The test is positive when no firm end point is palpated, greater than 1 mm of medial joint opening is noted (fluoroscopically), or there is reproduction of the patient's pain. Medial collateral ligament injuries may occur after trauma, such as an elbow dislocation, or as a repetitive overuse injury, commonly seen in overhead-throwing athletes. The typical history includes a pop and medial elbow pain following throwing activities, or patients may present with recurrent medial elbow pain, classically during the late cocking to early acceleration phase of throwing. Athletes typically complain of a progressive loss of velocity, accuracy, and endurance, which may be exacerbated by glenohumeral internal rotation deficits common to throwing athletes. The physical examination typically elicits tenderness over the MCL.