Infraspinatus Beneath the Skin

Description

Posterior shoulder anatomy is rendered with a translucent skin layer, exposing the scapula, proximal humerus, posterior ribs, and cervical spine as a framework for the rotator cuff. The infraspinatus occupies the infraspinous fossa inferior to the scapular spine, its fibers converging laterally toward a tendon that passes deep to the posterior deltoid to insert on the middle facet of the greater tubercle of the humerus. Superiorly, the muscle borders the spine of scapula and infraspinous fascia; medially it approaches the medial border of the scapula, while laterally it approaches the glenohumeral joint line and posterior capsule. Bone landmarks stay readable. External rotation mechanics and posterior shoulder pain workups depend on this relationship. Infraspinatus weakness and atrophy, classically seen with suprascapular nerve entrapment at the spinoglenoid notch or after traction injury, localize to the muscle belly in the infraspinous fossa, whereas a full thickness rotator cuff tear more often involves the supraspinatus but can extend posteriorly to the infraspinatus tendon footprint on the greater tubercle. The posterior view also maps the corridor used in posterior arthroscopic portals and in open posterior approaches, where the deltoid overlies the cuff and the plane between deltoid and infraspinatus guides safe access without violating the joint capsule prematurely. Use this artwork in upper limb gross anatomy and kinesiology teaching to link scapular surface anatomy to cuff insertions, and in orthopedic or sports medicine publications discussing rotator cuff tear patterns, suprascapular neuropathy, or posterior shoulder arthroscopy. It also suits patient education materials explaining why a tendon deep to the deltoid can generate lateral shoulder pain and weakness in external rotation. Anatomical accuracy verified by SciePro's Medical Advisory Board.