chap, xni.] REGION OF THE LLBOIV. 243 



rigidity of the elbow, due to reflex irritation from 

 disease, it is well to note that all the nerves of the 

 articulation supply muscles acting upon the joint, 

 notably, the musculo-spiral and musculo-cutaneous. 

 The relation of the ulnar nerve to the joint serves to 

 explain cases where severe pain has been felt along 

 the fore-arm and in the fingers, in parts corresponding 

 to the distribution of that nerve. The upper epiphysis 

 of the radius and the greater part of the upper 

 epiphyses of the humerns and ulna are intrasynovial, 

 i.e. come within the capsule of the joint. 



Dislocations of the elbow. These are many, 

 and may be thus arranged. (1) Dislocations of both 

 radius and ulna either backwards, outwards, inwards, 

 or forwards (in order of frequency). (2) Dislocations 

 of the radius alone either forwards, backwards, or 

 outwards (in order of frequency). (3) Luxation of 

 the ulna alone backwards. 



As a preliminary it may be convenient to note 

 some general anatomical considerations in connection 

 with these various displacements. 



(a) Antero-posterior htxations are much more 

 common than are lateral luxations. Displacements 

 in the antero-posterior direction are more common, 

 because the movements of the joint take place in that 

 direction, and the width of the articular surface of the 

 humerus from before backwards is comparatively small. 

 On the other hand, there is normally no lateral move- 

 ment of the elbow, and the width of the articulation 

 from side to side is considerable. The antero-posterior 

 ligaments are feeble, while the lateral ligaments are 

 strong, and the joint, moreover, receives more muscular 

 support at its sides than it does either behind or in 

 front. The mutual support afforded by the bones to one 

 another is weakened in the antero-posterior direction 

 during certain movements. Thus in full flexion the 

 olecranon has but a feeble hold upon the humerus, 



