The shoulder girdle is made up of three bones (scapula, collarbone, and collarbone). and humerus) and three joints (glenohumeral, acromioclavicular, and The shoulder has a greater range of motion than any other joint. It is also prone to large deltoid muscle injuries. help with shoulder movement Under this muscle are four rotator cuff muscles. (subscapularis, supraspinatus, infraspinatus, and less often teres) assist in shoulder movement and provide more stability. These muscles are attached to bones by tendons. The tendons are made up of the muscles and tendons that hold the forearm to the shoulder joint. A rotator cuff tear is a partial or complete tear of the rotator cuff. It is fairly common.