The Elbow-Joint, between the trochlear and capitellar surfaces of the humerus, and the sigmoid fossa of the ulna and depression on the head of the radius.

A hinge-joint permitting of movement round only one axis, viz.Transverse - flexion and extension.

Ligaments

The capsular ligament is complete and strengthened by various bands of fibres. It is attached to the upper-borders of the fossae on the anterior and posterior surfaces of the humerus and the lower aspects of the condyles (not enclosing them in the joint cavity), round the margin of the olecranon process and the inner and anterior margin of the coronoid process, and round the lower edge of the articular surface surrounding the head of the radius-i.e., just above the neck. It will thus be seen that the elbow-joint encloses within its cavity the superior radio-ulnar joint.

Fig. 7. The Elbow Joint.

Fig. 7. - The Elbow-Joint.

Anterior Ligament, from the upper margins of the coronoid and supracapitellar fossae on the humerus to the margin of the coronoid process and the orbicular ligament of the radio-ulnar joint. The fibres of this ligament are arranged in several directions to give strength.

Posterior Ligament, from the upper margin of the olecranon fossa of the humerus to the anterior margin of the upper aspect of the olecranon process of the ulna.

Internal Lateral Ligament is arranged in three parts, forming a triangle : (1) From anterior border of inner condyle to the margin of the coronoid process; (2) from the inferior and posterior border of the condyle to the olecranon process; ami (3) from the olecranon process to the coronoid process.

External Lateral Ligament, from the lower border of the outer condyle of the humerus to the orbicular ligament on the radius.

Muscles Acting On The Elbow-Joint

Action.

Muscle.

Origin.

Insertion.

Nerve-supply.

Flexion

Biceps

See Shoulder-Joint

Brachialis anticus

From lower two-thirds of anterior surface of shaft of humerus and the intermuscular septa, enclosing above the insertion of the deltoid

The rough tubercle on the anterior surface of the coronoid process of the ulna and the anterior ligament of the elbow-joint

Musculo-cuta-neus

Brachio-radialis

See Radio-Ulnar Joints

Pronator radii teres

See Radio-Ulnar Joints

Flexors of wrist and fingers

See Wrist and Phalang eal Joints

Extensors of wrist (during pronation)

See Wrist and Phalang eal Joints

Extension

Triceps

See Shoulder-Joint

Anconeus

From posterior surface of outer condyle of humerus

The outer surface of olecranon process, back of ulna and deep fascia

Musculo-spiral

Extensors of wrist and fingers during supination

Cartilage covers the articular surfaces of the joint as usual, but is not prolonged into the fossae on the humerus, where pads of fat are placed. There is also a narrow gap in the cartilage covering the surfaces of the olecranon and coronoid processes, thus separating the two.

The synovial membrane lines all the joint, including those parts not covered by cartilage, and is continuous with that lining the superior radio-ulnar joint.