RADIO ULNAR A R TICULA TION 



313 



Synovial Membrane. The synovial membrane (Fig. 256) of this articulation has been called, 

 from its extreme looseness, the membrana sacciformis. It projects horizontally inward between 

 the head of the ulna and the articular disk, and upward between the radius and the ulna, forming 

 a very loose cul-de-sac (recessus sacciformis). The quantity of synovia which it contains is usually 

 considerable. The inferior radioulnar joint does not communicate with the wrist-joint. 



Wrist-joint. 



Inferior radioulnar 

 articulation. 



Carpal articulations. 



Carpometacarpal 

 rticulations. 



FIG. 253. Ligaments of wrist and hand. Anterior view. 



Inferior radioulnar 



articulation 



Wrist-joint 



Carpal articulations 



Carpometacarpal 



articulations 



FIG. 254. Ligaments of wrist and hand. Posterior view. 



Movements. These consist of a movement of rotation through about 1 60 degrees of the lower 

 end of the radius around an axis which corresponds to the centre of the head of the ulna. When 

 the radius rotates forward, promotion of the forearm and hand is the result; and when backward, 

 snpination. It will thus be seen that in pronation and supination of the forearm and hand 

 the radius describes a segment of a cone, the axis of which extends from the centre of the head 



