The infraspinatus (Latin: musculus infraspinatus) is a flat, triangular shaped muscle of the shoulder girdle, belonging to the rotator cuff muscles.
The infraspinatus muscle originates from the walls of the infraspinous fossa on the posterior surface of the scapula.
The infraspinatus fills the infraspinous fossa of the scapula. The muscle fibers of the infraspinatus travel laterally and insert onto the greater tubercle of the humerus.
The infraspinatus stabilizes the glenohumeral joint and provides external rotation of the upper arm.
The infraspinatus is innervated by the suprascapular nerve (C5 - C6).
The blood supply to the infraspinatus muscle is largely provided by the supraspinatus artery and the circumflex scapular artery.