Shoulder Impingement
Normal Anatomy and Movement
The shoulder girdle is made up of 3 bones, the scapula (shoulder blade), the clavicle (collar bone) and the humerus (arm bone). The shoulder is a ball and socket joint, with the ball-shaped head of the humerus sitting just underneath the arch of the scapula. The space between the head of the humerus and the arch of the scapula is called the subacromial space.