124 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 201. — Sagittal section of frozen preparation of the left elbow -joint (i). 



Fig. 202. — A frozen section through the radiocarpal articulation parallel with the dorsal surface of the 

 hand (|). 



upon the other side it is attached to the styloid process of the ulna. In rare instances it is 

 perforated. 



The movement in the distal radio-ulnar joint is a rotation of the radius about the ulna which is simultaneously 

 carried out in the proximal radio-ulnar articulation also. During the movement known as pronation, the radius is applied 

 obliquely to the ulna, so that the two bones cross; the opposite movement, the return to the parallel position of the two 

 bones, is called supination. The axis of movement of both radio-ulnar articulations passes through the heads of both 

 bones and is consequently placed obliquely to the axes of the bones. The angle of rotation of the lower end of the radius 

 about the ulna amounts to about 180 degrees. 



THE JOINTS AND LIGAMENTS OF THE HAND, 



The joints of the hand may be divided into those of the carpus and those of the fingers. 

 Those of the carpus are: (i) The radiocarpal or wrist- joint; (2) the intercarpal joint; (3) the 

 joint 0} the pisiform bone; (4) the common carpo-metacarpal joint; (5) the car po- metacarpal 

 joint of the thumb. 



The joints of the fingers include the metacar po- phalangeal articulations and digital or inter- 

 phalangeal articulations. 



THE JOINTS OF THE CARPUS. 



The radiocarpal articulation, the articulation of the pisiform bone, and the carpo-meta- 

 carpal articulation of the thumb are usually independent joints, while the common carpo-meta- 

 carpal articulation is, as a rule, connected with the intercarpal joint. 



The radiocarpal articulation is the joint between the carpal articulating surface of the 

 radius and the triangular articular disc interposed between the ulna and the triquetral (cunei- 

 form) bone upon one side, and the proximal articular facets of the first row of carpal bones — 

 navicular (scaphoid), lunatum (semilunar), and triquetrum (cuneiform) — upon the other, the 

 navicular and lunate bones articulating with the radius and the triquetrum (cuneiform) bone 

 with the triangular articular disc in such a manner that the radius and the disc together form 

 a socket, while the corresponding articular facets of the three carpal bones form a condyle. 



The articulation is completely separated from the intercarpal joint, but in rare instances 

 it communicates with the articulation of the pisiform bone. It is separated from the intercar- 

 pal articulation by the short ligaments connecting the navicular, the lunate, and the triquetral 

 (cuneiform) bones. 



The articular capsule of the joint is thin, capacious, and relaxed, and embraces the car- 

 tilaginous extremities of the bones entering into the articulation. 



From the shape of its articulating surfaces the radiocarpal articulation is an ellipsoidal 

 joint. The curvature of the surfaces is greater in the sagittal than in the coronal diameter. 



The intercarpal articulation is the joint between the two rows of carpal bones and is formed 

 by the distal articular facets of the navicular, lunate, and triquetral (cuneiform) bones upon 



