The shoulder consists of two primary bones: the scapula and the humerus, which is the long bone of the upper arm. The scapula features a socket known as the glenoid, into which the head of the humerus fits, creating a versatile ball-and-socket joint. This bone has an unusual shape, extending upwards and around the back of the shoulder joint to form a roof called the acromion, and at the front to form the coracoid process. The shoulder joint is cushioned by cartilage covering the glenoid socket and the head of the humerus. Stability is provided by a fibrous cartilage ring surrounding the glenoid socket, known as the labrum. Ligaments link the shoulder bones, while tendons connect these bones to the surrounding muscles. The biceps tendon attaches the biceps muscle to the shoulder, contributing to joint stability. Additionally, four short muscles originating from the scapula encircle the shoulder, with their tendons merging to create the rotator cuff.