The shoulder is susceptible to both acute injuries and chronic conditions since it's highly mobile. To make your CPT coding as simple as possible, try to get a good idea of the shoulder's key anatomical features. Start off with the bones: The bones that form the shoulder girdle are the humerus, clavicle, scapula, and sternum. The largest shoulder joint is the glenohumeral joint while the acromioclavicular joint (AC) and the sternoclavicular joint (SC) are smaller joints of the shoulder. The glenoid labrum is a fibrous tissue rim that increases 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. Know the clock-face analogy: Looking at a cross-section of the gleno-humeral joint, oftentimes surgeons describe some of their procedures by analogy to a clock face. Therefore, you may see the labrum was torn between 4 and 6 o'clock. If you think of 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. Often, orthopedists use the clock-face analogy to describe tears of the labrum or work carried out on some sections of the glenohumeral joint capsule. The rotator cuff is an important pain point: The rotator cuff is a series of four muscles – subscapularis, suprasinatus, infraspinatus and teres minor - that hold the humeral head in the glenoid socket. The subscapularis is the largest muscle and is anterior while the supraspinatus is the muscle most commonly torn and is superior. The posterior muscles are the infraspinatus and teres minor. You may even see the term ‘the rotator interval'. This is the space between the anterior edge of the supraspinatus and the superior edge of the subscapularis, and is the only space where the rotator cuff doesn't invest the glenohumeral joint completely.