Shoulder Joint: Anatomy, Function & Rotator Cuff

Shoulder The joint formed by the meeting of the upper arm bone (humerus) with the shoulder blade (scapula) and collar bone (clavicle). The ball of the upper arm bone fits roughly into the shallow cup formed by the shoulder socket of the shoulder blade. This allows the arm to move in many directions. At the shoulder, the rotator cuff tendons help move the arm and keep the ball in the socket.