RADIOCARPAL ARTICULATION OR WRIST-JOINT 



327 



segment of a cone, the axis of which extends from the center of the head of the radius to the 

 middle of the head of the ulna. In this movement the head of the ulna is not stationary, but 

 describes a curve in a direction opposite to that taken by the head of the radius. This, however, 

 is not to be regarded as a rotation of the ulna the curve which the head of this bone describes 

 is due to a combined antero-posterior and rotatory movement, the former taking place almost 

 entirely at the elbow-joint, the latter at the shoulder-joint. 



Wrist-joint 



Radial collateral 

 ligament 



Distal radioulnar 

 articulation 



Articular disc 



Ulnar collateral ligament 



Pisiform 



FIG. 336. Vertical section through the articulations at the wrist, showing the synovial cavities. 



VI. Radiocarpal Articulation or Wrist-joint (Articulatio Radiocarpea) 



(Figs. 334, 335). 



The wrist-joint is a condyloid articulation. The parts forming it are the lower 

 end of the radius and under surface of the articular disk above; and the navicular, 

 lunate, and triangular bones below. The articular surface of the radius and the 

 under surface of the articular disk form together a transversely elliptical concave 

 surface, the receiving cavity. The superior articular surfaces of the navicular, 

 lunate, and triangular form a smooth convex surface, the condyle, which is received 

 into the concavity. The joint is surrounded by a capsule, strengthened by the 

 following ligaments: 



The Volar Radiocarpal. 

 The Dorsal Radiocarpal. 



The Ulnar Collateral. 

 The Radial Collateral. 



The Volar Radiocarpal Ligament (ligamentum radiocarpeum volare; anterior liga- 

 ment) (Fig. 334). This ligament is a broad membranous band, attached above 

 to the anterior margin of the lower end of the radius, to its styloid process, and to 

 the front of the lower end of the ulna; its fibers pass downward and medialward 

 to be inserted into the volar surfaces of the navicular, lunate, and triangular 

 bones, some being continued to the capitate. In addition to this broad mem- 

 brane, there is a rounded fasciculus, superficial to the rest, which reaches from the 

 base of the styloid process of the ulna to the lunate and triangular bones. The 

 ligament is perforated by apertures for the passage of vessels, and is in relation, 

 in front, with the tendons of the Flexor digitorum profundus and Flexor pollicis 



