It involves an articulation between the glenoid fossa of the scapula (shoulder blade) and the head of the humerus (upper arm bone).

[3] Synovium extends below the long head of biceps and subscapularis tendon to form subscapular bursa.

[5] The tendon of the long head of the biceps brachii passes through the bicipital groove on the humerus and inserts on the superior margin of the glenoid cavity to press the head of the humerus against the glenoid cavity.

[4] The supraspinatus, infraspinatus and teres minor muscles aid in abduction and external rotation.

The rotator cuff muscles of the shoulder produce a high tensile force, and help to pull the head of the humerus into the glenoid cavity.

Such an imbalance could cause a forward head carriage which in turn can affect the range of movements of the shoulder.

The capsule can become inflamed and stiff, with abnormal bands of tissue (adhesions) growing between the joint surfaces, causing pain and restricting the movement of the shoulder, a condition known as frozen shoulder or adhesive capsulitis.

In younger people, these dislocation events are most commonly associated with fractures on the humerus and/or glenoid and can lead to recurrent instability.

The contrast should not enter subacromial bursa unless supraspinatus tendon is completely ruptured.