Anatomy of the Shoulder JointThe shoulder joint as such is not a single joint but a combination of many different joints. It includes the following joints 1. Scapulo-thoracic joint 2. Acromio-clavicular joint 3. Sterno-clavicular joint 4. Geno-humeral joint
All these joints act together during movements of the shoulder. Here we are mainly concerned with the Geno-humeral joint (joint between the head of humerus and the glenoid cavity ). Hence from now on the word shoulder joint will mean the Geno-humeral joint. 
This is the main joint connecting the upper limb to the torso. It is a ball and socket type of synovial joint. It permits movement is all directions, but at the cost of bony stability, because the head of humerus is large and the glenoid cavity is small and shallow. Stability is provided by other structures that include 1. Coracoacromial arch 2. Rotator cuff 3. Glenoid labrum 4. Muscles such as the long head of biceps. 
The coracoacromial arch is formed by bony coracoid and acromian processes of the scapula and a ligament connecting these called the coracoacromial ligament. Below this arch passes the rotator cuff. 
Between the coracoacromial arch and the rotator cuff is a bursa called Subacromial bursa. It is the largest bursa of the body and its function is to allow smooth movement, of the rotator cuff tendons, below the coracoacromial arch when the arm is moved over head.
The rotator cuff is an important structure that is formed by the union of four muscular tendons. These muscles originate from the scapula (shoulder blades) and attach on the upper end of humerus. This cuff stabilizes the shoulder in all directions except inferiorly. The cuff is located below the coracoacromial arch.
The tendon of long head of biceps is partly located inside the joint. Close to the humerus it is found in the bicipital groove. This is a bony channel through which the tendon passes. In this confined space, it is most susceptible to inflammation. Now it will be much easier for you to understand the different causes of shoulder pain. Recurrent Shoulder Dislocation Go back to Shoulder Pain from Shoulder Joint Anatomy
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