Infraspinatus Muscle, Gross Anatomy

Description

Seen from a posterior aspect of the male shoulder, the infraspinatus occupies the infraspinous fossa of the scapula, its fibers coursing superolaterally toward the greater tubercle of the humerus at the glenohumeral joint. Superior to it lies the scapular spine (and the supraspinous region), while inferiorly the muscle approaches the lateral border of the scapula and the posterior axillary fold. The deltoid overlays the rotator cuff laterally, wrapping from the scapular spine and acromion toward its humeral insertion, with portions of the cervical and upper thoracic vertebrae and posterior ribs forming the medial and deep backdrop. A clear lateral relationship to the humeral head is emphasized. Posterior rotator cuff anatomy is where external rotation strength, dynamic glenohumeral stability, and many common shoulder complaints intersect. The infraspinatus tendon, inserting on the middle facet of the greater tubercle, is frequently involved in posterosuperior cuff tears and tends to retract posteromedially toward the scapular fossa, a pattern surgeons assess when planning arthroscopic repair and when estimating the risk of fatty infiltration. Compression or irritation at the suprascapular nerve can also present as infraspinatus weakness with relatively preserved deltoid bulk, and this view helps clarify why lesions at the spinoglenoid notch selectively denervate infraspinatus while sparing supraspinatus. Palpable and testable. Use this artwork to support musculoskeletal anatomy courses covering the scapulohumeral rhythm and rotator cuff force couples, or to illustrate clinical teaching on the external rotation lag sign and posterior shoulder pain patterns. It also suits orthopedic and sports medicine publications discussing cuff tear morphology, tendon retraction, and arthroscopic portal orientation relative to the scapular spine and humeral head. Anatomical accuracy verified by SciePro's Medical Advisory Board.