Summary Anconeus Origin Lateral epicondyle of humerus Insertion Lateral surface of olecranon and superior part of posterior surface of ulna Action Assists triceps in extending forearm (terminal 15° of extension and supination); stabilizes elbow joint; abducts ulna during pronation Innervation Radial nerve (C7, C8, T1) Arterial supply Medial collateral artery; recurrent posterior interosseous artery, posterior branch of radial collateral artery