Infraspinatus Muscle as, Posterior View

Description

Posteriorly, the scapulae sit lateral to the thoracic spine and ribs, with the humeral heads articulating at the glenoid fossae. Filling the infraspinous fossa below the scapular spine, the infraspinatus muscle forms a broad triangular belly that narrows laterally toward its tendon on the greater tubercle of the humerus, adjacent to the posterior aspect of the glenohumeral joint capsule. Superior to it, the supraspinatus occupies the supraspinous fossa, so the two rotator cuff muscles frame the scapular spine while the clavicles remain anterior landmarks seen at the shoulder girdle margins. Bone and muscle align clearly. Rotator cuff teaching often blurs individual tendons, and the posterior view corrects that by separating infraspinatus from supraspinatus along the scapular spine and clarifying their shared insertion neighborhood on the greater tubercle. Clinically, the infraspinatus is a primary external rotator and a key dynamic stabilizer against posterior translation of the humeral head, and its weakness is classically screened with resisted external rotation and the external rotation lag sign in suspected posterosuperior cuff tears. This angle also helps explain why suprascapular nerve entrapment at the spinoglenoid notch can selectively denervate infraspinatus, producing posterior shoulder pain and isolated external rotation weakness without major supraspinatus deficit. Use this artwork in gross anatomy and kinesiology modules on the scapulohumeral rhythm, in orthopaedic or sports medicine texts discussing rotator cuff tear patterns, and in patient education materials that need a clean posterior map for injection planning or post-operative rehabilitation cues after cuff repair. Anatomical accuracy verified by SciePro's Medical Advisory Board.