The infraspinatus muscle is one of the muscles that makes up the rotator cuff. It originates on the infraspinous fossa of the scapula, and inserts on the middle facet of the greater tubercle of the humerus. It functions to externally rotate the humerus and to stabilize the head of the humerus in the glenoid cavity during upward movement of the arm. Trigger points in this muscle refer pain deep into the anterior shoulder joint and down the anterior arm. Trigger points near the lower medial border refer pain into the rhomboids. This muscle is often injured during throwing motions.