THE WRIST-JOINT 



267 



the apex of the articular disc. Some of the fibres pass forward and laterally to 

 the base of the pisiform bone and to the medial part of the upper border of the 

 transverse carpal ligament, where it is attached to the pisiform bone; they form 

 a thick, rounded fasciculus on the front of the wrist. Other fibres descend 

 vertically to the medial side of the triquetral bone, and others again laterally to 

 the dorsal surface of the triquetral. The tendon of the extensor carpi ulnaris is 

 posterior to, and passes over, part of the fibres of the ligament. 



The radial collateral ligament (fig. 300) consists of fibres which radiate from 

 the fore part and tip of the styloid process of the radius. Some pass downward 

 and medially, in front, to the navicular and adjacent edge of the capitate; some 

 downward, a little forward and medially, to the tubercle of the navicular and 

 ridge of the greater multangular; and others downward and laterally to the 

 rough dorsal surface of the navicular. 



The fibres of this ligament are not so long and strong, nor do they radiate so much as those 

 of the ulnar collateral ligament. It is in relation with the radial artery, and the abductor pollicis 

 longus {extensor ossis metacarpi pollicis) and extensor pollicis brevis, the artery separating the 

 tendons from the ligament. 



Fig. 301. — Posterioe View of Wrist. 



Dorsal radio-carpal ligament 



Capsule of carpo-metacarpal 

 joint of thumb 



Posterior radio -ulnar ligament 



Ulnar collateral ligament of 

 wrist 



The synovial membrane is extensive, but does not usually communicate with 

 the synovial membrane of the inferior radio-ulnar joint, being shut out by the 

 articular disc. It is also excluded, in almost every instance, from that of 

 the carpal joints by the interosseous ligaments between the first row of carpal 

 bones. The styloid process of the radius is cartilage-covered medially, and 

 forms part of the articular cavity, while that of the ulna does not. 



The arterial supply is derived from the anterior and posterior carpal rami, the dorsal 

 division of the volar interosseous, and from twigs direct from the radial and ulnar arteries. 



The nerve -supply is derived from the ulnar and median in front, and the deep branch of 

 the radial (posterior interosseous) behind. 



Relations. — In front of the radio-carpal joint are the tendons of the flexor muscles of the 

 wrist and fingers, the synovial sheaths associated with them, the radial and ulnar arteries, and 

 the median and ulnar nerves. 



Behind the joint are the majority of the tendons of the extensor muscles of the wrist and 

 fingers, with their synovial sheaths, the terminal part of the anterior and posterior interosseous 

 arteries, and the deep branch of the radial nerve (posterior interosseous). On the radial side 

 lie the tendons of the abductor pollicis longus {extensor ossis metacarpi pollicis) and the extensor 

 pollicis brevis. On the ulnar side the joint is subcutaneous and it is crossed by the dorsal 

 cutaneous branch of the ulnar nerve. tj. n 



Movements. — The wrist is a condyloid joint, the carpus forming the condyle. It allows 

 of movements upon a transverse axis, i. e., flexion and extension; and around an antero-pos- 

 terior axis, i. e., abduction and adduction; together with a combination of these in quick succes- 



