Articular Circumference Of The Radial Head, Posterior View

Description

Radial head anatomy is centered on the articular circumference, the smooth peripheral rim that encircles the proximal radius at the level of the humeroradial and proximal radioulnar joints. From a posterior perspective, the circular contour of the radial head is read as a continuous band that lies superior to the radial neck and immediately lateral to the ulna’s radial notch (incisura radialis ulnae), where the annular ligament would normally clasp the rim. The posterior aspect of the proximal radius provides a stable bony reference for appreciating how uniformly the articular margin must be contoured to permit low-friction pronation and supination. No guesswork here. Clinical relevance concentrates on the rim. Marginal radial head fractures (often Mason type I or II) and osteochondral defects can disrupt this articular circumference, producing painful forearm rotation despite preserved elbow flexion and extension, and subtle step-offs at the rim can explain mechanical catching that is easy to miss on limited radiographic projections. This fixed posterior viewpoint helps you teach the concept of a continuous, congruent ring: the same surface that must remain smooth against the annular ligament and the radial notch, while the superior fovea of the head interfaces with the capitulum of the humerus. It also supports discussions of instability patterns, including posterolateral rotatory instability and the role of the radial head as a secondary stabilizer in valgus stress when the medial collateral ligament complex is compromised. Use this illustration in upper limb anatomy courses when introducing the proximal radioulnar joint, or in orthopedics and sports medicine materials addressing radial head fracture classification, operative indications, and expected motion loss after malunion. It also fits radiology teaching files that correlate rim irregularity with limitation of pronation and supination on exam. Anatomical accuracy verified by SciePro's Medical Advisory Board.