Shoulder Anatomy

The shoulder is the most mobile joint in the human body, allowing a wide range of motion in multiple planes. This remarkable mobility comes from the coordination of several structures working together, but it also makes the shoulder vulnerable to injury.

The shoulder complex consists of three bones: the clavicle (collarbone), scapula (shoulder blade), and humerus (upper arm bone). These bones form three joints: the glenohumeral joint (the main ball-and-socket), the acromioclavicular (AC) joint, and the sternoclavicular (SC) joint.

The rotator cuff is a group of four muscles and their tendons (supraspinatus, infraspinatus, teres minor, and subscapularis) that surround the shoulder joint. These muscles work together to stabilize the humeral head within the glenoid socket and enable rotation and elevation of the arm.

The glenoid labrum is a ring of fibrocartilage that surrounds the glenoid (socket) of the shoulder. It deepens the socket by up to 50%, providing stability to the joint. The labrum also serves as an attachment point for the biceps tendon and several ligaments.