Origin: Infraspinous fossa of scapula.

Insertion: Posterior aspect of greater tubercle of humerus and capsule of shoulder joint.

Isolated function: Assists in concentric acceleration of external rotation of the humerus.

Integrated function: 
-Assists in eccentric deceleration of internal rotation of the humerus.
-Works synergistically with the other rotator cuff musculature to dynamically stabilize the humeral head in the glenoid fossa during functional movements
-Works synergistically to produce dynamic caudal glide of the humeral head in the glenoid fossa during elevation.
-Works as an intergrated functional unit with the capsule, ligaments, and other cuff musculature to enhance stability and proprioception during functional movements (ligamento-muscular protective reflex).

Nerve Supply: Subscapular, C4, 5, 6.