A 19-year-old baseball pitcher develops medial elbow pain during late cocking, with tenderness over the medial epicondyle and pain on the moving valgus stress test. Which structure is primarily at fault?

• A Annular ligament
• B Lateral ulnar collateral ligament
• C Anterior band of the ulnar collateral ligament ✓
• D Posterior bundle of the ulnar collateral ligament

Explanation

Valgus stress during throwing is resisted mainly by the anterior band of the ulnar collateral ligament, which is taut between 30 and 120 degrees of flexion. Repetitive microtrauma causes attenuation or rupture, producing medial pain in late cocking and early acceleration. The lateral ulnar collateral ligament resists varus stress and posterolateral rotatory instability, so it cannot explain a valgus-extension overload pattern in a pitcher.

Reference: Miller's Review of Orthopaedics, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.