Shoulder joint

The shoulder joint (or glenohumeral joint from Greek glene, eyeball, + -oid, 'form of', + Latin humerus, shoulder) is structurally classified as a synovial ball and socket joint and functionally as a diarthrosis and multiaxial joint. It involves articulation between the glenoid cavity of the scapula (shoulder blade) and the head of the humerus (upper arm bone).Diagram of the human shoulder joint, front viewDiagram of the human shoulder joint, back viewThe left shoulder and acromioclavicular joints, and the proper ligaments of the scapula.Dissection image of coracohumeral ligament of glenohumeral joint in green.Dissection image of cartilage of glenohumeral joint in green. The shoulder joint (or glenohumeral joint from Greek glene, eyeball, + -oid, 'form of', + Latin humerus, shoulder) is structurally classified as a synovial ball and socket joint and functionally as a diarthrosis and multiaxial joint. It involves articulation between the glenoid cavity of the scapula (shoulder blade) and the head of the humerus (upper arm bone). Due to the very loose joint capsule that gives a limited interface of the humerus and scapula, it is the most mobile joint of the human body. The shoulder joint is a ball and socket joint between the scapula and the humerus. However the socket of the glenoid cavity of the scapula is itself quite shallow and is made deeper by the addition of the glenoid labrum. The glenoid labrum is a ring of cartilaginous fibre attached to the circumference of the cavity. This ring is continuous with the tendon of the biceps brachii above. Significant joint spaces are: The axillary space is an anatomic space between the associated muscles of the shoulder. This space transmits the subscapular artery and axillary nerve. The shoulder joint has a very loose joint capsule known as the articular capsule of the humerus and this can sometimes allow the shoulder to dislocate. The long head of the biceps brachii muscle travels inside the capsule from its attachment to the supraglenoid tubercle of the scapula. Because the tendon of the long head of the biceps brachii is inside the capsule, it requires a tendon sheath to minimize friction. A number of small fluid-filled sacs known as synovial bursae are located around the capsule to aid mobility: The supra-acromial bursa does not normally communicate with the shoulder joint.