the infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa. As one of the four muscles of the rotator cuff. Supraspinatus, Infraspinatus, Subscapularis, and Teres Minor together This Four Muscle work as rotatory to the Humerus. so also known as Rotator Cuff . Infraspinatus ORIGIN: the infraspinatus originates from infraspinous fossa of the scapula. Infraspinatus INSERTION: the infraspinatus is inserted at greater tubercle of humerus, posterior to supraspinatus. Infraspinatus ACTION: helps to hold the head of the humerus in glenoid cavity. stabilizes the shoulder joint. rotates humerus laterally. Infraspinatus NERVE SUPPLY: the infraspinatus muscle is supplied by the Suprascapular nerve.