26 HANDBOOK OF ANATOMY 



The Triangular Mbro- Cartilage separates the two joints ; it is. 

 attached by its apex to the outer surface of the styloid process 

 of the ulna, and by its base to the edge of the inner surface of 

 the lower end of the radius below its articulation with the 

 ulna. 



Ligaments. The capsule is very imperfect, consisting of a few 

 transverse fibres which* connect the bones ventrally and dorsally. 



The synovial membrane lines the joint and passes over the 

 .upper surface of the triangular fibro-cartilage. 



The Interosseous Membrane is a strong fibrous membrane 

 stretched between the radius and ulna, and attached to their 

 inter osseous borders. Above, it extends to within about an inch 

 of the head of the radius, leaving a gap for the passage of the 

 dorsal inter osseous vessels ; below, it reaches down to the ex- 

 tremities of the bones. The direction of the fibres is downwards 

 from the radius to the ulna. 



The Wrist (Radio-Carpal) Joint between the distal end of the 

 radius and the triangular fibro-cartilage, and the proximal row 

 of carpal bones. 



The joint is a condyloid one, capable of movement through 

 two axes : 



Antero-posterior flexion and extension. 



Transverse abduction and adduction. 



In the ordinary position of the hand the end of the radius and 

 articular disc are in contact with the scaphoid and semilunar 

 bones, but in adduction (the hand bent to the ulnar side) the 

 cuneiform bone is pushed outward and comes in contact with 

 the triangular fibro-cartilage instead of the capsule of the joint. 



Ligaments. A capsule completely surrounds the joint, and is 

 attached to the edges of the articular surfaces, and is carried up 

 to the edge of the lower end and styloid process of the ulna. It 

 has well-defined strengthened portions. 



Anterior Carpal ligament, attached above, to the lower edge 

 of the radius, the styloid process of the ulna, and the anterior 

 border of the triangular fibro-cartilage; below, to the palmar 

 surfaces of the scaphoid, semilunar, and cuneiform bones. Some 

 fibres may be carried on to the os magnum. 



Posterior-carpal ligament, attached above to the lower end of 



