142 ARTICULATIONS OF THE UPPER LIMB. 



THE WRIST- JOINT AND ARTICULATIONS OF THE HAND. 



THE RADIO-CARPAL ARTICULATION, or wrist-joint, is formed between the 

 radius and triangular fibre-cartilage above, and the scaphoid, semilunar and 

 cuneiform bones below. The superior surface, concave both transversely and 

 from before backwards, is subdivided by linear elevations into three parts cor- 

 responding to the three bones below, the innermost part being formed by the 

 fibro-cartilage. The inferior surface, convex in both directions, is prolonged 

 further down upon the carpal bones behind than in front. 



The internal lateral ligament is a rounded cord passing directly down- 

 wards from the extremity of the styloid process of the ulna, to be attached 

 to the cuneiform bone ; it also sends some fibres to the anterior annular 

 ligament and the pisiform bone. 



The external lateral ligament extends from the styloid process of the 

 radius to a rough surface on the outer side of the scaphoid bone, some of 

 its fibres being prolonged to the trapezium, and also to the anterior annular 

 ligament of the wrist. 



The anterior ligament (radio-carpal), broad and membranous, consists 

 partly of fibres which have a nearly transverse direction, partly of others, 

 which diverge as they descend from the anterior border of the radius to the 

 scaphoid, semilunar, and cuneiform bones : some of them are continued to 

 the os magnum. 



The posterior ligament extends obliquely downwards and inwards, from 

 the extremity of the radius, to the posterior surface of the first row of the 

 carpal bones, especially the cuneiform bone ; its fibres are prolonged some 

 distance on the surface of the carpal bones. 



The synovial membrane is reflected from the radius and the triangular 

 fibro-cartilage, on the surrounding ligaments, and, after lining these, passes 

 to the opposed surface of the carpal bones. 



THE CARPAL ARTICULATIONS. The bones of the carpus, the pisiform 

 excepted, are so arranged in two rows, that while only slight movement can 

 take place between the members of each row, a considerable amount of 

 movement is possible between the two rows. The surface presented by the 

 first row to the second is concave both transversely and from before back- 

 wards in the greater part of its extent, but at its outer side it is bounded by 

 the convex part of the scaphoid bone. The opposing surface of the second 

 row is concavo-convex from without inwards, the concavity being formed by 

 the trapezium and trapezoid, the convexity by the os magnum and unciform 

 bone. 



The two rows of carpal bones are united by dorsal, palmar, and lateral 

 ligaments. The lateral ligaments are placed one at the radial, the other at 

 the ulnar border of the carpus ; the former connects the scaphoid bone with 

 the trapezium, the latter the cuneiform with the unciform. The dorsal 

 ligaments consist of fibres passing in various directions ; the palmar ligaments 

 are chiefly composed of fibres converging towards the os magnum. 



The bones of the first row, the pisiform bone excepted, are united by inter- 

 osseous, and by dorsal and palmar ligaments. The interosseous ligaments, 

 placed on the sides of the semilunar bone on a level with its superior sur- 

 face, connect it with the scaphoid and cuneiform bones, thus completing the 

 inferior wall of the radio-carpal joint. The dorsal and palmar ligaments, 

 each two in number, extend transversely on the dorsal and palmar surfaces 

 from the scaphoid bone to the semilunar, and from the semilunar to the 

 cuneiform. 



