Secondary tensor and supinator muscles of the human proximal radio-ulnar joint.

A gross anatomical study was made of the human elbow. Three very small muscles were found that are not described in contemporary anatomical publications. A lateral tensor muscle of the annular ligament was observed in seven of every ten cadavers; its action is to tense or pull the annular ligament laterally during supination. A medial tensor muscle of the annular ligament was found in two of every ten cadavers; its action is to tense the annular ligament, pulling it medially and distally, and to assist in supination. An accessory supinator muscle was found in four of ten cadavers; its action is to assist in supination. These muscles would be synergistic to the primary supinator muscles of the radio-ulnar joint.