The shoulder complex is a ball and socket joint and is comprised of 4 main muscles, several bones, and several soft tissue structures. The scapula (shoulder blade), clavicle (collar bone), and humerus (upper arm bone) make up the bony components. The primary muscles of the shoulder can be divided into two groups called scapulothoracic and scapulohumeral. The scapulothoracic muscles help stabilize the shoulder complex to the thoracic spine or mid back are comprised of the trapezius, rhomboids and serratus anterior. The scapulohumeral muscles consist of the main movers of the shoulder joint the rotator cuff and deltoid. The rotator cuff (supraspinatus, infraspinatus, teres minor and subscapularis) and deltoid work together to provide additional stability and function to the shoulder complex.