THE RADIOCARPAL OR WRIST-JOINT 139 



fibers above; this lowest split between the ligament and ulna 

 is filled with fat and covered by the pronator quadratus muscle. 

 Some fibers go to the posterior annular ligament. 



The Inferior Radioulnar Articulation 



This is a lateral ginglymus joint between the head of the 

 ulna and sigmoid cavity of the radius. 



The ligaments are the anterior and posterior radioulnar and 

 triangular fibrocartilage The anterior and posterior ligaments 

 are narrow bands passing transversely over the joint, as indi- 

 cated by their names. 



The triangular ligament is placed beneath the ulna, attached 

 by its apex to the base of the styloid process; its under surface 

 articulates with the cuneiform. 



The synovial membrane is very extensive, the membrana 

 sacciformis. 



Actions are supination and pronation. 



THE ARTICULATIONS OF THE WRIST AND CARPUS 

 The Radiocarpal or Wrist- joint 



This is a condyloid articulation between the radius and 

 triangular cartilage above, the scaphoid, semilunar, and cunei- 

 form below. 



The ligaments are external and internal lateral, anterior and 

 posterior. The first two are rounded cords passing respectively 

 from the styloid process of the radius and ulna to the end 

 carpal bones of the first row. The anterior ligament is a broad 

 membranous band connecting the anterior surfaces of the 

 bones forming the articulation. The posterior ligament is 

 less strong than the anterior, and passes from the radius to 

 the dorsum of the first three carpals. 



Nerves are from the ulnar and posterior interosseous. 



Actions are flexion, extension, abduction, adduction, and 

 circumduction. 



