Infraspinatus Muscle Under the Skin, Posterior View

Description

Across the posterior shoulder girdle, the infraspinatus forms a broad triangular mass deep to the skin, occupying the infraspinous fossa of the scapula inferior to the scapular spine and lateral to the vertebral border. Its fibers run superolaterally toward the greater tubercle of the humerus, lying deep to the posterior deltoid laterally and bordered inferiorly by teres minor and teres major near the lateral border of the scapula. Medially, the trapezius spans from the occiput and thoracic spinous processes toward the scapular spine and acromion, creating a clear relationship between superficial scapular stabilizers and the deeper rotator cuff. Surface contours matter here. Posterior views that keep the skin intact are the ones clinicians use mentally during palpation, injection planning, and surgical positioning, and they make the infraspinatus footprint easier to relate to scapular landmarks such as the spine and acromion. Infraspinatus weakness or atrophy points you toward suprascapular nerve pathology, often at the spinoglenoid notch, where ganglion cysts associated with posterior labral tears can selectively denervate the infraspinatus while sparing the supraspinatus. When teaching rotator cuff tears, this perspective clarifies why loss of external rotation strength and posterior shoulder pain can track back to a muscle that sits mostly under the scapular spine, not on the lateral arm. Use this illustration in gross anatomy and kinesiology modules to connect scapular positioning, trapezius function, and rotator cuff force couples, and in sports medicine or orthopedics materials discussing posterior shoulder pain, external rotation testing, and arthroscopic portals around the posterior deltoid. It also suits patient education sheets where a posterior shoulder map needs to stay realistic because the skin surface remains visible. Anatomical accuracy verified by SciePro's Medical Advisory Board.