anconeus

Short, triangular arm muscle closely associated with the distal end of the triceps brachii on the posterior surface of the humerus. Its origin is on the lateral epicondyle of the humerus, and its insertion is on the lateral aspect of the olecranon process and posterior ulna. The anconeus abducts the ulna during forearm pronation and it acts as a synergist of the triceps brachii during elbow extension.