Infraspinatus Muscle

Description

Seen from the posterior shoulder girdle of an adult female, the infraspinatus occupies most of the infraspinous fossa on the dorsal surface of the scapula, its fibers running laterally and slightly superiorly toward the humeral head. Along its inferior border sit teres minor superiorly and teres major more inferiorly, while the posterior deltoid caps the lateral shoulder, partly overlapping the rotator cuff. Superiorly, trapezius spans the posterior neck and scapular spine region, with rhomboid major and minor positioned deep and medial to retract the scapula. Latissimus dorsi forms the inferolateral back contour. Lateral convergence of the infraspinatus onto its tendon at the greater tubercle (middle facet) is the teaching point here, because this is the primary external rotator of the glenohumeral joint and a key dynamic stabilizer against anterior translation. Tear patterns in the posterosuperior cuff and fatty atrophy of infraspinatus are common imaging findings, and the muscle is a frequent target for strength testing (external rotation lag sign) when evaluating rotator cuff pathology. Compression of the suprascapular nerve at the spinoglenoid notch can selectively denervate the infraspinatus, producing isolated infraspinatus wasting, a clinical distinction that hinges on recognizing its posterior scapular footprint. A common pitfall. Use this artwork in gross anatomy and kinesiology modules to tie scapular surface anatomy to rotator cuff biomechanics, and in orthopedics or sports medicine publications discussing rotator cuff tendinopathy, posterosuperior cuff tears, or suprascapular neuropathy. It also suits patient education materials for shoulder pain where a posterior approach or palpation landmarks need clear orientation. Anatomical accuracy verified by SciePro's Medical Advisory Board.