Annular Ligament of the Radius, Lateral View

Description

Seen from the lateral aspect of the male elbow, the annular ligament forms a fibrous ring encircling the radial head and apposing it to the radial notch of the ulna, creating the proximal radioulnar joint immediately distal to the capitulum of the humerus. The radiocapitellar (radiohumeral) articulation sits superior to the ligament, with articular cartilage indicated on the capitulum and radial head to emphasize the contact surfaces during forearm rotation. Laterally, the radial collateral ligament blends with the annular ligament near the lateral epicondyle, reinforcing the capsule while remaining separate from the ulnohumeral hinge line. Forearm pronation and supination depend on the radial head rotating within this annular ring while maintaining congruence with the capitulum, so a clean lateral view helps clarify why stability does not require locking the radius to the ulna. This anatomy has immediate clinical relevance in nursemaid’s elbow (radial head subluxation), where longitudinal traction on the pronated forearm can allow the radial head to slip partially out from under the annular ligament, producing acute refusal to use the limb. It also frames the mechanism of posterolateral rotatory instability when lateral collateral complex injury permits pathologic external rotation and subluxation at the radiocapitellar joint. Small structure, big consequences. Use this illustration in gross anatomy and musculoskeletal anatomy teaching to explain proximal radioulnar mechanics, or in orthopaedic and emergency medicine materials covering radial head subluxation reduction maneuvers and lateral elbow ligament injuries. It also suits surgical education focused on lateral approaches to the elbow, where preserving the annular ligament and its relationship to the radial collateral fibers helps maintain postoperative stability. Anatomical accuracy verified by SciePro's Medical Advisory Board.