ARTICULATIONS OF THE CARPUS 317 



The ligaments are: 



Anterior. External Lateral. 



Posterior. Internal Lateral. 



The anterior or palmar ligaments (ligamenta intercarpea volaria) consist of 

 short fibres, which pass, for the most part, from the palmar surface of the bones 

 of the first row to the front of the os magnum. 



The posterior or dorsal ligaments (ligamenta intercarpea dorsalis) consist of 

 short, irregular bundles of fibres passing between the bones of the first and second 

 row on the dorsal surface of the carpus. 



The lateral ligaments are very short; they are placed, one on the radial, the 

 other on the ulnar side of the carpus; the former, the stronger and more distinct, 

 connecting the scaphoid and trapezium, the latter the cuneiform and unciform; 

 they are continuous with the lateral ligaments of the wrist-joint. In addition to 

 these ligaments, a slender interosseous band sometimes connects the os magnum 

 and the scaphoid. 



Synovial Membrane (Fig. 256). The synovia! membrane of the carpus is very extensive; 

 it passes from under the surface of the scaphoid, semilunar, and cuneiform bones to the upper 

 surface of the bones of the second row, sending upward two prolongations between the scaphoid 

 and semilunar and the semilunar and cuneiform; sending downward three prolongations between 

 the four bones of the second row, which are further continued onward into the carpometacarpal 

 joints of the four inner metacarpal bones, and also for a short distance between the metacarpal 

 bones. There is a separate synovial membrane between the pisiform and the cuneiform bones. 



Movements. The articulation of the hand and wrist, considered as a whole, is divided into 

 three parts: (1) The radius and the articular disk, (2) the meniscus, 1 formed by the scaphoid, 

 semilunar, and cuneiform, the pisiform bone having no essential part in the movements of the 

 hand; (3) the hand proper, the metacarpal bones with the four carpal bones on which they are 

 supported viz., the trapezium, trapezoid, os magnum, and unciform. These three elements 

 form two joints: (1) The superior, wrist-joint proper, between the meniscus and bones of the 

 forearm; (2) the inferior, transverse or midcarpal joint, between the hand and meniscus. 



1. The articulation between the forearm and carpus is a true condyloid articulation, and 

 therefore all movements but rotation are permitted. Flexion and extension are the most exten- 

 sive, and of these a greater amount of extension than flexion is permitted on account of the 

 articulating surfaces extending farther on the dorsal than on the palmar aspect of the carpal 

 bones. In this movement the carpal bones rotate on a transverse axis drawn between the tips 

 of the styloid processes of the radius and ulna. A certain amount of adduction (or ulnar flexion) 

 and abduction (or radial flexion) is also permitted. Of these movements, the former is consider- 

 ably greater in extent than the latter. In these movements the carpus revolves upon an antero- 

 posterior axis drawn through the centre of the wrist. Finally, circumdudion is permitted by 

 the consecutive movements of adduction, extension, abduction, and flexion, with intermediate 

 movements between them. There is no rotation, but this is provided for by the supination and 

 pronation of the radius on the ulna. The movement of flexion is performed by the Flexor carpi 

 radialis, the Flexor carpi ulnaris, and by the Palmaris longus; extension, by the Extensor carpi 

 radialis longior et brevior and the Extensor carpi ulnaris; adduction (ulnar flexion), by the Flexor 

 carpi ulnaris and the Extensor carpi ulnaris; and abduction (radial flexion), by the Extensors of 

 the thumb and the Extensores carpi radialis longior et brevior and the Flexor carpi radialis. 



2. The chief movements permitted in the transverse or midcarpal joint are flexion, extension, 

 and a slight amount of rotation. In flexion and extension, which are the movements most freely 

 enjoyed, the trapezium and trapezoid on the radial side and the unciform on the ulnar side 

 glide forward and backward on the scaphoid and cuneiform respectively, while the head of the 

 os magnum and the superior surface of the unciform rotate in the cup-shaped cavity of the 

 scaphoid and semilunar. Flexion at this joint is of greater range than extension. A very trifling 

 amount of rotation is also permitted, the head of the os magnum rotating around a vertical axis 

 drawn through its own centre, while at the same time a slight gliding movement takes place in 

 the lateral portions of the joint. 



1 Called meniscus because the bones composing it serve the essential purposes of an articular disk. 



