Infraspinatus
| Pronuncation | in-fruh-spine-ATE-us |
| Derivation | Below (infra) the spine (of the scapula). |
| Origin | A wide area on the surface of the scapula below the spine. |
| Insertion | Posterior side of the head of the humerus. |
| Action | Rotates the upper arm laterally (outward). |
Infraspinatus forms a flat, oblique bulk on the scapula when tensed. Though triangular, with fibers running toward the point of the shoulder, about half of the muscle is covered by deltoid and its triangularity can only be hinted at in a drawing.
Teres ("TEH-reez") minor is a small muscle running along with the outer edge of infraspinatus. It can be safely grouped with its larger neighbor, and the break between them is visible but rarely.