Definition: the shoulder joint is a synovial joint of the ball and socket variety.
Articulating surfaces:
I. Head of the humerus
II. Glenoid cavity of the scapular
The glenoid labrum, a ring of cartilage, attached to the margins of the glenoid cavity, deepens the depression of the glenoid cavity.
Capsule: this is very large and it is attached to the scapula beyond the supraglenoid tubercle and margins of the articular margin of the head (anatomical neck) except inferiorly where it is attached to the surgical neck of the humerus.
Synovial membrane: this is attached along the glenoid labrum and lines the capsule. It is attached to the surgical neck of the humerus.
Intrinsic ligaments: this are thickenings of the fibrous capsule which strengthen the shoulder joint.
1. Glenohumeral ligament
2. Transverse humeral ligament
3. Coracohumeral ligament
4. Coracoacromial ligament.
Blood supply:
1. Branches of the anterior and posterior circumflex humeral arteries from the axillary artery.
2. Suprascapular artery from the subclavian.
Nerve supply: branches of the Suprascapular, axillary, and lateral pectoral nerves.
Movement: the joint permits flexion, extension, abduction, adduction, circumduction and rotation of the upper limb.
Stability: this depends on the strength of the surrounding muscles:
1. The closely related rotator cuff muscles
2. Long head of biceps
3. More distantly located long muscles of the shoulder e.g deltoid, long head of triceps, latissimus dorsi, pectoralis major and trees major.
Clinical correlates:
1. Dislocation of the shoulder joint
2. Rupture of the rotator cuff muscles