A posterior view of the shoulder girdle showing three muscles: supraspinatus m., infraspinatus m., and teres minor m. They each help the humerus move in different ways:
Suprapinatus m.: 'Helps deltoid abduct arm at shoulder; stabilizes shoulder by drawing humerus toward glenoid fossa of scapula'
Infraspinatus m.: 'Laterally rotates arm at shoulder; stabilizes shoulder by drawing humerus toward glenoid fossa of scapula'
Teres minor m: 'Laterally rotates and weakly adducts arm at shoulder; draws humerus toward glenoid fossa of scapula to help stabilize the shoulder'
- Info from Get Body Smart .com [link]