The acromio-clavicular ligament joins the acromion process to the clavicle.

The coraco-clavicular ligament joins the coracoid process to the clavicle.

The coraco-acromial ligament joins the coracoid process to the acromion process.

The ligaments of the shoulder-joint are :

1.  Capsular.                     3. Gleno-humeral.

2.  Coraco-humeral.          4. Glenoid.

The capsular ligament envelops the joint, being attached to the margin of the glenoid cavity and ligament, and to the outer part of the anatomical neck of the humerus. The tendon of the long head of the biceps passes through an opening in it, at the top of the bicipital groove, to its attachment at the apex of the glenoid cavity. Synovial membrane lines the interior of the capsular ligament, and is reflected from it upon the head of the humerus.

The coraco-humeral ligament is a broad band attached to the coracoid process, and to the tuberosities of the humerus.

The gleno-humeral ligament is within the joint.

The glenoid ligament is the rim of fibro-cartilage which deepens the cavity.

The shoulder is a ball and socket joint, and is capable of the movements of:

(1)  Flexion, forward movement ;

(2)  Extension, backward movement;

(3)  Abduction, outward movement ;

(4)  Adduction, inward movement ;

(5)  Circumduction, which includes all the previous movements ;

(6)  Rotation, a movement of the bone on its own axis, in

which it is not carried away from the body as in circumduction.

Between the acromion process and the capsule of the shoulder-joint there is a large bursa, the sub-acromial, by which the neighbouring surfaces are lubricated, and the movements of the upper end of the humerus facilitated.

Beside the two processes which overhang the head of the humerus, and the long tendon of biceps which crosses it, the joint is further strengthened and the bones kept in position by muscles from the back of the scapula, which also cross over and are inserted into the three facets of the greater tuberosity of the humerus. They are the supra-spinatus from above the spine of the scapula, inserted into the uppermost of the facets, the infra-spinatus from below the spine of the scapula inserted into the middle facet, and the teres minor from the axillary border of the scapula inserted into the lowest facet. The former supports the joint from above, the two latter from behind. In front is the subscapularis from the anterior of the scapula, which has insertion into the lesser tuberosity. Below, it receives partial support from the long head of the triceps, a muscle on the back of the arm inserted into the lower part of the glenoid cavity, and the teres major, coming from the inferior angle of the scapula to insertion into the inner ridge of the bicipital groove. It is important to bear in mind that this is the least supported part of the joint. Abduction of the arm should be very carefully performed in a case of previous downward dislocation. Atmospheric pressure also helps to keep the bones in position. The blood-supply of the joint is from the supra-scapular and posterior circumflex. The nerve-supply is the supra-scapular and circumflex.

The ligaments of the elbow are in the form of a capsule which surrounds the joint on all sides. They are the

(1) External lateral,                   (3) Anterior,

(2) Internal lateral,                     (4) Posterior.

The external lateral ligament is a short strong band attached to the lower part of the external condyle of the humerus, to the outer side of the olecranon process of the ulna and to the orbicular ligament of the radius.

The internal lateral ligament is attached to the internal condyle of the humerus, and to the coronoid and olecranon processes of the ulna. The anterior ligament is attached to the humerus above the coronoid fossa and to the coronoid process of the ulna and the orbicular ligament of the radius.

The posterior ligament is attached to the humerus above the olecranon fossa, to the olecranon process and the orbicular ligament.

Synovial membrane lines the capsule, and is reflected upon the bones which are enclosed within the ligaments. It lines the radial, coronoid, and olecranon fossae and goes down to the superior radio-ulnar joint. Movements of this joint are flexion and extension. A bursa intervenes between the tendon of biceps and tuberosity of radius.

The blood-supply of this joint is derived from the anastomosis of vessels surrounding the joint. The nerve-supply is the ulnar, median and musculo-spiral.

The orbicular ligament mentioned before as surrounding the neck of the radius is the special ligament of the superior radio-ulnar-joint. There is an anterior and posterior ligament passing from the radius to the ulnar in connection with the inferior radio-ulnar joint. In this joint the synovial membrane forms a loose sac and extends some distance between the radius and ulna. In the superior radio-ulnar joint the synovial membrane continued from the elbow-joint lines the orbicular ligament. The movements of supination and pronation take place at the radio-ulnar joints. At the superior joint the head of the radius rotates within the orbicular ligament, moving on the capitellum of the humerus. At the inferior joint the lower end of the radius revolves round the lower end of the ulna. In supination the palm of the hand is upwards, the thumb outwards, and the two bones of the forearm parallel. In pronation the palm is downwards, the thumb inwards, and the radius lies across the ulna. The ligaments of the wrist are the

(1) Anterior,                     (3) Internal lateral,

(2) Posterior,                    (4) External lateral.

The anterior ligament is attached to the anterior margin of the lower end of the radius and ulna, and to the palmar surface of the scaphoid, semilunar, and cuneiform bones.

The posterior ligament is attached to the posterior border of the lower end of the radius, and to the dorsal surface of the scaphoid, semilunar, and cuneiform bones.

The internal lateral ligament is attached to the styloid process of the ulna, and to the inner side of the cuneiform and pisiform bones.

The external lateral ligament is attached to the styloid process of the radius, and to the outer side of the scaphoid and trapezium.

They form a capsule round the joint, and are continuous with each other. Dorsal, palmar, and interosseous ligaments pass transversely between the individual bones of both rows, and also dorsal, palmar, lateral, and interosseous ligaments pass from one row to the other. The movements of this joint are flexion, extension, abduction, adduction and circumduction.

Blood-supply, radial and ulnar arteries ; nerve-supply, ulnar and posterior interosseous nerves.

The four metacarpal bones are united by dorsal and palmar ligaments at their bases.

The transverse metacarpal ligament unites the heads of the metacarpal bones and prevents excessive separation from each other.

Synovial Membrane.—The pisiform, and the upper metacarpal joint of the thumb, have each a separate synovial membrane. The other carpal and metacarpal joints have a single synovial membrane.

The first row of joints formed by the heads of the metacarpal bones, and the first phalanx of the fingers, are ball and socket joints, and are capable of flexion, extension, abduction, adduction and circumduction. The second and third rows are simple hinge-joints, and are limited to flexion and extension.

These joints have each a palmar and two lateral ligaments, the deep surfaces of which are lined with synovial membrane.