Learn what's where to make your coding easier Because the shoulder is highly mobile, it is particularly suscep-tible to both acute injuries and chronic conditions. To make your CPT coding as simple as possible, you should try to get a good idea of the shoulder's major anatomical features. Start with the bones: The bones that form the shoulder are the humerus, clavicle and scapula. The glenohumeral joint is the largest shoulder joint, and the acromioclavicular joint (AC) and the sternoclavicular joint (SC) are smaller joints of the shoulder. The glenoid labrum is a fibrous tissue rim that improves the stability of the glenohumeral joint and attaches the glenohumeral ligaments and the biceps tendon to the glenoid (or the end of the scapula). The biceps tendon attaches the biceps muscle to the shoulder. Learn the clock-face analogy: Looking at a cross-section of the glenohu-meral joint, surgeons often describe some of their procedures by analogy to a clock face. Thus, you may see -The labrum was torn between 4 and 6 o-clock.- If you imagine a clock face superimposed on the cross-section of the glenoid fossa only, on the right shoulder the anterior aspect of the joint will be from 12 to 6, while on the left shoulder the posterior aspect will be from 12 to 6. Orthopedists often use the clock-face analogy to describe tears of the labrum or work done on certain sections of the glenohumeral joint capsule. The rotator cuff is a major pain point: The rotator cuff is a series of four muscles that hold the humeral head in the glenoid socket. The muscles are the 1) subscapularis, 2) supraspinatus, 3) infraspinatus and 4) teres minor. The subscapu-laris is the largest muscle and is anterior. The supra-spinatus is the muscle most commonly torn and is superior. The infraspinatus and teres minor are the posterior muscles. You may also see the term -the rotator interval.- This is the space between the ante-rior edge of the supraspinatus and the superior edge of the subscapularis, and is the only space where the rotator cuff does not completely invest the glenohu-meral joint.