WRIST JOINT. 125 



The internal lateral ligament extends from the styloid process of 

 the ulna to the cuneiform and pisiform bone. 



The external lateral ligament is attached by one extremity to the 

 styloid process of the radius, and by the other to the side of the 

 scaphoid bone. The radial artery rests on this ligament as it 

 passes backwards to the first metacarpal space. 



The synovial membrane of the wrist joint lines the under surface 

 of the radius and interarticular fibro-cartilage above, and the first 

 row of bones of the carpus below. 



The relations of the wrist joint are the flexor and extensor ten- 

 dons by which it is surrounded, and the radial and ulnar artery. 



Actions. The movements of the wrist joint are flexion, extension, 

 adduction, abduction, and circumduction. In these motions the arti- 

 cular surfaces glide upon each other. 



Articulations between the Carpal Rones. These are amphi-arthro- 

 dial joints, with the exception of the conjoined head of the os mag- 

 num and unciforme, which is received into a cup formed by the 

 scaphoid, semilunar, and cuneiform bones, and constitutes an enar- 

 throsis. The ligaments are, 



Dorsal, 

 Palmar, 

 Interosseous, 

 Anterior annular. 



The dorsal ligaments, are ligamentous bands, that pass from bone 

 to bone in every direction, upon the dorsal surface of the carpus. 



The palmar ligaments are fasciculi of the same kind, but 

 stronger than the dorsal, having the like disposition upon the palmar 

 surface. 



The interosseous ligaments are situated between the adjoining 

 bones in each range : in the upper range they close the upper 

 part of the spaces between the scaphoid, semilunar, and cuneiform 

 bones ; in the lower range they are stronger than in the upper, and 

 connect the os magnum on the one side to the unciforme, on the 

 other to the trapezoides, and leave intervals through which the 

 synovial membrane is continued to -the bases of the metacarpal 

 bones. 



The anterior annular ligament is a firm ligamentous band, which 

 connects the bones of the two sides of the carpus. It is attached 

 by one extremity to the trapezium and scaphoid, and by the other 

 to the unciform process of the unciforme and the base of the pisi- 

 form bone, and forms an arch over the anterior surface of the 

 carpus, beneath which the tendons of the long flexors and the 

 median nerve pass into the palm of the hand. 



The articulation of the pisifwm bone with the cuneiform, is pro- 

 vided with a distinct synovial membrane, which is protected by 

 fasciculi of ligamentous fibres, forming a kind of capsule around the 

 joint ; they are inserted into the cuneiforme, unciforme, and base of 

 the metacarpal bone of the little finger. 



