The shoulder is an important joint and has the most mobility of all joints in the body. The shoulder is able to move forwards, backwards, and in a circular motion away from the body. There are many structural components that make up the shoulder and when one part is functioning improperly, it may cause pain and inability to move the joint. The shoulder is a ball and socket joint and is composed of 3 bones, the humerus, the clavicle, and the scapula. In addition to bones, the shoulder is also made up of cartilage, muscles and tendons. Some of the most common injuries of the shoulder include, rotator cuff injury and frozen shoulder.