CAEPAL JOINTS. 



329 



. 



Anterior radio- 

 ulnar ligament 



Pisiform bone 



Capitate bone, with 

 ligaments radiat- 

 ing from it 

 Hamulus of 

 os hamatum 



Collateral radio-carpal 

 ligament 



Tubercle of navicular 



bone 



Ridge on 

 greater mult- 

 angular bone 

 Greater 

 multangular 

 bone 



FIG. 310. LIGAMENTS ON VOLAR ASPECT OF RADIO-CARPAL, 

 CARPAL, AND CARPO-METACARPAL JOINTS. 



of the radius, as well as slightly to the base of the styloid process of the ulna. 



Some transverse 



fibres may be seen, 



but the greater num- 



ber pass obliquely dis- 



tally and medially to 



. J . J . 



the VOlar nOn-artlC- 



ular surfaces of the 

 navicular, lunate, and Medial 

 triquetral bones, while- 

 some of them may 

 even be continued as 

 far as the capitate 

 bone. Those fibres 

 from the ulna run 

 obliquely laterally. 

 On its deeper aspect 

 this ligament is closely 

 adherent to the volar 

 border of the articular 

 disc of the distal radio- 

 ulnar articulation. 



Lig. Radiocar- 

 peum Dorsale. The 

 dorsal radio-carpal 

 ligament (O.T. poster- 

 ior ligament) extends 

 from the dorsal margin 

 of the distal end of the radius, in an oblique direction distally and medially, to the 

 dorsal non-articular areas on the proximal row of the carpal bones. The slip to the 

 latter assists in forming the fibrous sheath through which the tendon of the ex- 

 tensor carpi ulnaris muscle travels to its insertion. The principal bundle of fibres 

 is connected with the triquetral bone. 



The stratum synoviale (Fig. 311) is simple, and is confined to the articulation, 

 except in those cases in which the articular disc is perforated, or in which 

 one of the interosseous ligaments between the carpal bones of the first row is absent. 

 The epiphyseal lines at the distal ends of radius and ulna are extra-capsular. 



Movements at the Radio-carpal Joint. The radio-carpal joint affords an excellent example 

 of a bi-axial articulation, in which a long transverse axis of movement is situated more or less at 

 right angles to a short axis placed in the antero-posterior direction. The nature of the move- 

 ments which are possible around these two axes is essentially the same in both cases, viz., flexion 

 and extension. The movements around the longer transverse axis are anterior or volar flexion, 

 extension, and its continuation into dorsi-flexion. Around the shorter antero-posterior axis we get 

 movements which result from combined action by certain flexor and extensor muscles, whereby 

 the radial or ulnar borders of the hand may be approximated towards the corresponding borders 

 of the forearm. Lateral movement also may be possible to a slight extent. The range of move- 

 ment in connexion with either of the principal axes is largely a matter of individual peculiarity, 

 for, with the exception of the lateral ligaments, there is no serious obstacle to the cultivation' of 

 greater mobility at the radio-carpal joint. 



ARTICULATIONES INTERCARPE^. 



Carpal Joints. The articulations subsisting between the individual carpal 

 bones are all diarthroses, and although the total amount of movement through- 

 out the series is considerable, yet the extent of movement which is possible 

 between the two rows or between any two carpal bones is extremely limited. 

 For this reason, as well as because of the nature of the movement, these articula- 

 tions are called gliding joints (arthrodia). 



It is advisable to consider, first, the articulations between individual bones of 

 the proximal row; second, the articulations between the separate bones of the 

 distal row ; third, the articulation of the proximal and distal rows with each other ; 

 fourth, the pisiform articulation. 



