Origin Supraspinous fossa of scapula Insertion Superior facet on greater tuberosity of humerus Action Initiates abduction of the arm from 0-15°, then assists deltoid in abduction of arm after 15° to 90°, and finally stabilizes head of the humerus in the glenoid cavity Innervation Suprascapular nerve (C4, C5 and C6) (C4, C5, C6) Arterial Supply Suprascapular artery