Rotator cuff repair shoulder surgery, illustration. The rotator cuff is a group of muscles and tendons that stabilize the shoulder. The shoulder joint is seen from the top here, looking down on the head of the humerus as it articulates with the glenoid socket of the scapula (shoulder blade). The sutures used to repair these muscles and tendons vary according to the size of the tear being operated on. This is a major suture, used for a very large tear.