126 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 203. — Articulations and ligaments of the hand seen from the dorsal surface (J). 



Fig. 204. — Articulations and ligaments of the hand seen from the volar surface, the transverse carpal 



ligament having been removed (£). 

 Fig. 205. — Articulations of the middle finger seen from the side (J). 



In the movements of the hand the radiocarpal and intercarpal articulations act together as hinge joints. The four 

 chief movements of the hand are flexion, extension, radial flexion (or, better, radial abduction), and ulnar flexion (or, 

 better, ulnar abduction). By a combination of these movements it is possible to effect an almost complete circumduc- 

 tion of the hand. 



The chief movements of the joints are flexion and extension. The axes of rotation of the two hinge joints are not 

 placed at right angles to the axis of the forearm, but obliquely and intersecting each other.* During flexion of the radio- 

 carpal articulation, the hand deviates to the radial side; during the similar movement in the intercarpal articulation 

 the hand deviates to the ulnar side and vice versa. If one joint is flexed and the other extended, the movements in the 

 axis of the extremity neutralize each other, while the lateral movements (radial or ulnar abduction, as the case may be) 

 are more pronounced. If both joints are flexed or extended together, the lateral movements neutralize each other and 

 the movements in the axis of the extremity (flexion or extension) are more pronounced. 



The carpo-metacarpal articulations are arthrodia and are but slightly movable; this is particularly true of the 

 carpo-metacarpal joints of the second and third fingers. They move slightly when the concavity of the hand is increased 

 or diminished, that is to say, during hollowing or flattening of the palm, and during opposition of the little finger. 



The range of motion of the carpo-metacarpal joint of the thumb is much more extensive. Like all saddle joints 

 it is biaxial, but owing to the incongruity of the articulating surfaces, the curvatures of one of the surfaces being always 

 more pronounced than those of the other, the movements about the two axes may be so combined that actual circum- 

 duction is possible. The chief movements of this joint are abduction (away from the index-finger), adduction (toward 

 the index-finger), and opposition (bringing the thumb opposite to the little finger). During the latter motion the con- 

 cavity of the palm is markedly increased. 



THE CARPAL LIGAMENTS. 



The carpal ligaments (Figs. 203 and 204) are composed of the ligaments between the bones 

 of the forearm and the carpal bones and of those which connect the carpal bones with each 

 other and with the bases of the metacarpal bones. 



Of the first group, the ligaments which connect the ulna with the carpus are weak, while 

 the radius is connected to the carpus by strong ligaments. It will be remembered that the carpal 

 bones articulate with the radius only. 



The only ligament arising from the ulna is the ulnar lateral ligament (Figs. 203 and 204), 

 which passes from the styloid process of the ulna to the triquetral (cuneiform) bone. The 

 corresponding ligament upon the radial side is the radial lateral ligament (Figs. 202 and 204) 

 which passes from the styloid process of the radius to the navicular bone. The radius is con- 

 nected to the carpus also by two strong ligaments which reinforce the dorsal and palmar sur- 

 faces of the capsule. 



The dorsal radiocarpal ligament (Fig. 203) passes obliquely from the lower end of the radius 

 to the dorsal surface of the first row of carpal bones and is attached particularly to the triquetral 

 (cuneiform) bone. The corresponding anterior ligament, the volar radiocarpal ligament (Fig. 

 204), is longer than the dorsal one; it arises from the margin of the articular surface of the carpus 

 and is inserted not only into the bones of the first row, but also into the capita turn (os magnum). 



* This description of the movements of the hand has been materially modified by the more recent studies of these 

 articulations. It must not be supposed that the two rows of carpal bones cannot move upon each other; during radial 

 abduction the navicular bone is markedly moved toward the adjacent bones. 



