Anatomy of the Shoulder

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The shoulder is made up of several layers, including the following:

• Bones. The collarbone (clavicle), the shoulder blade (scapula), and the upper arm bone (humerus).

• Joints. Facilitate movement, including the following:

  • Sternoclavicular joint (where the clavicle meets the sternum)

  • Acromioclavicular (AC) joint (where the clavicle meets the acromion)

  • Shoulder joint (glenohumeral joint). A ball-and-socket joint that facilitates forward, circular, and backward movement of the shoulder.

• Ligaments. A white, shiny, flexible band of fibrous tissue that holds joints together and connects various bones, including the following:

  • Joint capsule. A group of ligaments that connect the humerus to the socket of the shoulder joint on the scapula to stabilize the shoulder and keep it from dislocating.

  • Ligaments that attach the clavicle to the acromion

  • Ligaments that connect the clavicle to the scapula by attaching to the coracoid process

• Acromion. The roof (highest point) of the shoulder that is formed by a part of the scapula.

• Tendons. The tough cords of tissue that connect muscles to bones. The rotator cuff tendons are a group of tendons that connect the deepest layer of muscles to the humerus.

• Muscles. Help support and rotate the shoulder in many directions.

• Bursa. A closed space between two moving surfaces that has a small amount of lubricating fluid inside; located between the rotator cuff muscle layer and the outer layer of large, bulky muscles.

• Rotator cuff. Composed of tendons, the rotator cuff (and associated muscles) holds the ball of the glenohumeral joint at the top of the upper arm bone (humerus).