76 THE SUPERIOR EXTREMITY 



surface of the proximal row of carpal bones forms a surface 

 which is convex from side to side and fits into a correspondingly 

 concave surface provided by the carpal aspect of the radius 

 and the articular disc. In this way radial and ulnar deviation 

 of the hand are rendered possible. The capsule is strengthened 

 by: 



(i) .The Volar and (2) Dorsal Radio -Carpal Ligaments, 

 which are attached to the margins of the articular surfaces ; 

 they are weak bands., but they receive additional support from 

 the flexor and extensor tendons. 



FIG. 27. Section through the Carpus, to show the various Joint Cavities. 



Light blue = articular cartilage. Green = periosteum. 



Striped blue = ligaments. Red = synovial membrane. 



(3) The Radial Collateral (External Lateral) Ligament 

 passes from the tip of the radial styloid to the lateral surface of 

 the navicular and is crossed by the second part of the radial 

 artery. 



(4) The Ulnar Collateral (Internal) Ligament is attached 

 to the tip of the ulnar styloid and to the medial side of the 

 triquetrate (cuneiform) bone. It is on these collateral ligaments 

 that the strength of the joint depends. 



The Synovial Membrane lines the interior of the capsule 

 closely ; it requires no special description. 



Aspiration of the joint may be carried out immediately 



