RADIO-ULNAR ARTICULATION. 



153 



Fig. 87.* 



Fi: 



ter being extended from within outwards to the orbicular ligament, into 

 which they are attached inferiorly. This ligament is covered in by the 

 brachialis anticus muscle. 



The posterior ligament is a broad and 

 loose layer passing between the posterior 

 surface of the humerus and the anterior 

 surface of the base of the olecranon, and 

 connected at each side with the lateral 

 ligaments. It is covered in by the ten- 

 don of the triceps. 



The internal lateral ligament is a thick 

 triangular layer, attached above, by its 

 apex, to the internal condyle of the hu- 

 merus ; and below, by its expanded bor- 

 der, to the margin of the greater sigmoid 

 cavity of the ulna, extending from the 

 coronoid process to the olecranon. At 

 its insertion it is intermingled with some 

 transverse fibres. The internal lateral 

 ligament is in relation posteriorly with 

 the ulnar nerve. 



The external lateral ligament is a strong 

 and narrow band, which descends from 

 the external condyle of the humerus, to 

 be inserted into the orbicular ligament, 



and into the ridge on the ulna, with which the posterior part of the latter 

 ligament is connected. This ligament is closely united with the tenaon 

 of origin of the supinator brevis muscle. 



The synovial membrane is extensive, and is reflected from the cartila- 

 ginous surfaces of the bones upon the inner surface of the ligaments. It 

 surrounds inferiorly the head of the radius, and forms an articulating sac 

 between it and the lesser sigmoid notch. 



The muscles immediately surrounding, and in contact with, the elbow 

 joint, are in front, the brachialis ^anticus ; to the inner side, the pronator 

 radii teres, flexor sublimis digitorum, and flexor carpi ulnaris ; externally, 

 the extensor carpi radialis brevior, extensor cornmunis digitorum, entensor 

 carpi ulnaris, anconeus, and supinatcr brevis ; and behind, the triceps. 



Actions. The movements of the elbow joint are flexion and extension, 

 which are performed with remarkable precision. The extent to which 

 these movements are capable of being effected, is limited in front by the 

 coronoid process, and behind by the olecranon. 



6. The Radio-ulnar Articulation. The radius and ulnar are firmly held 

 together by ligaments which are connected with both extremities of the 

 bones, and with the shaft ; they are, the 



Orbicular, Anterior inferior, 



Oblique, Posterior inferior, 



Interosseous, Interarticular nbro-cartilage. 



* An internal view of the ligaments of the elbow joint. 1. The anterior ligament. 

 2. The internal lateral ligament. 3. The orbicular ligament. 4. The oblique ligament. 

 5. The interosseous ligament. G. The internal condyle of the humerus, which conceal* 

 the posterior ligament. 



j- An exterral view of the elbow joint. 1. The humerus. 2. The ulna. 3. The ra 



