Postero-lateral instability of the elbow joint is a rare clinical condition, commonly related to a disruption of the lateral collateral ligament complex of the elbow. Twenty elbow joint specimens were studied in order to describe the morphologic characteristics of this complex, and to determine the role of its different components in the stability of the elbow. After a morphologic and morphometric investigation, serial divisions of the medial bundle of the lateral collateral ligament were performed, with or without section of the annular ligament and the anterior bundle of the lateral collateral ligament. The anterior and medial bundles of the lateral collateral ligament had close relationships with the annular ligament and a common proximal course. Isolated section of the medial bundle of the lateral collateral ligament induced only minor laxity of the elbow joint. Combined divisions of the medial and the anterior bundles at their humeral insertion, or the medial bundle and the annular ligament at their ulnar insertion resulted in a reproducible subluxation of the ulno-humeral joint. Thus, postero-lateral rotatory stability of the elbow joint is largely maintained by the lateral collateral ligament complex, composed of three elements: the anterior and medial bundles of the lateral collateral ligament, and the annular ligament. In clinical practice, chronic postero-lateral instability is best treated by a ligamentous reconstruction, that must take into account all these anatomic considerations. We report here a new technique of ligamentoplasty using the fascia of the extensor carpi ulnaris muscle.