The infranaspinatus muscle is a large triangular shaped muscle that connects the infraspinatous fossa of the scapular laterally to the humerus. It is one of the muscles of the rotator cuff.


The infraspinatus muscle is responsible for external rotation of the humerus. The infrispinatus and teres minor work together to rotate the head of the humerus laterally.

The infraspinatus inserts at the infraspinatous fossa of the scapula laterally to the middle facet of the greater tubercle of the humerus.
The infraspinatus is the main external rotator of the shoulder. It synergises with the teres minor, and both also help in moving the arm backwards (extension).