262 



THE ARTICULATIONS 



VII. Radio-carpal or Wrist-joint. 



The Wrist is a condyloid articulation. The parts entering into its formation 



are the lower end of the radius and under surface 

 of the interarticular fibro-cartilage, which form 

 together the receiving cavity, and the scaphoid, 

 semilunar, and cuneiform bones, which form the 

 condyle. The articular surface of the radius and 

 the under surface of the inter-articular fibro-car- 

 tilage are the receiving cavity, forming together 

 a transversely elliptical concave surface. The 

 articular surfaces of the scaphoid, semilunar, and 

 cuneiform bones form together a smooth, convex 

 surface, the condyle, which is received into the 

 concavity above mentioned. All the bony sur- 

 faces of the articulation are covered with cartilage, 

 and connected together by a capsule, which is 

 divided into the following ligaments : 



External Lateral. Anterior. 



Internal Lateral. Posterior. 



The External Lateral Ligament (radio-carpal) 

 (Fig. 174) extends from the summit of the styloid 

 process of the radius to the outer side of the 

 scaphoid, some of its fibres being prolonged to the 

 trapezium and annular ligament. 



The Internal Lateral Ligament (ulno-carpat) is 

 a rounded cord, attached, above, to the extremity 

 of the styloid process of the ulna, and dividing 

 below into two fasciculi, which are attached, one 

 to the inner side of the cuneiform bone, the other 

 to the pisiform bone and annular ligament. 



The Anterior Ligament is a broad membranous 

 band, attached, above, to the anterior margin of 

 the lower end of the radius, its styloid process and 

 the ulna : its fibres pass downward and inward to 

 be inserted into the palmar surface of the scaphoid, 

 semilunar, and cuneiform bones, some of the fibres 

 being continued to the os magnum. In addition 

 to this broad membrane, there is a distinct 

 rounded fasciculus, superficial to the rest, which 

 passes from the base of the styloid process of the 

 ulna to the semilunar and cuneiform bones. This 

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

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

 Flexor longus pollicis ; behind, with the synovial membrane of the Avrist-joint. 



The Posterior Ligament (Fig. 175), less thick and strong than the anterior, is 

 attached, above, to the posterior border of the lower end of the radius ; its fibres 

 pass obliquely downward and imvard, to be attached to the dorsal surface of the 

 scaphoid, semilunar, and cuneiform bones, being continuous with those of the 

 dorsal carpal ligaments. This ligament is in relation, behind, with the extensor 

 tendons of the fingers ; in front, with the synovial membrane of the wrist. 



The Synovial Membrane (Fig. 177) lines the inner surface of the ligaments 

 above described, extending from the lower end of the radius and interarticular 

 fibro-cartilage above to the articular surfaces of the carpal bones below. It is 

 loose and lax, and presents numerous folds, especially behind. 



Relations. The wrist-joint is covered in front by the flexor and behind by the 

 extensor tendons ; it is also in relation Avith the radial and ulnar arteries. 



PH 



FIG. 176. Longitudinal section of the 

 right forearm, hand, and third finger, 

 viewed from, the ulnar aspect. (After 

 Braune.) 



