Understanding how the layers are arranged helps to understand how problems arise. The deepest layer includes the bones and the joints of the shoulder, followed by the ligaments that make up the joint capsule of the shoulder. The bones of the shoulder include the humerus , the scapula , and the clavicle . The roof of the shoulder is formed by a part of the scapula called the acromion . There are several important ligaments about the shoulder.
Ligaments are soft tissue structures that connect bones to bones.
The joint capsule is made by a group of ligaments that connect the humerus to the socket of the shoulder joint on the scapula. These ligaments are the main source of stability for the shoulder, and help to keep the shoulder from dislocating. There are also ligaments that attach the clavicle to the acromion, and two ligaments that connect the clavicle to the scapula by attaching to the coracoid process. The tendons and muscles are the next layer out from the joint. The first layer of muscles that move the shoulder are the rotator cuff muscles .