chap, xix.] THE HIP JOINT. 445 



4. Sooner or later, in hip disease, the thigh 

 becomes adducted and inverted, while it still remains 

 flexed. This position has been variously accounted 

 for. According to one theory, it is due to 

 softening and yielding of some parts of the inflamed 

 capsule. This view is set forth by Mr. Barker, in 

 his admirable monograph on joint disease in Holmes' 

 " System of Surgery," in the following words : 

 " As the inflamed capsule commences to soften, its 

 weakest part yields first, i.e., the posterior inferior 

 This now admits of more flexion still. . . . The hori- 

 zontal posterior fibres, which in the distended condition 

 of the capsule help in the eversion, are the next to 

 stretch, admitting of inversion, which is now the more 

 possible, as the Y is relaxed by flexion, and its inner 

 limb has no strain to be taken off by eversion. Finally, 

 the upper and outer anterior fibres yield, and adduction 

 then takes place." This explanation is a little 

 unsatisfactory ; and it is more probable that this false 

 position, and especially the adduction, depends upon 

 muscular action. The muscles about the joint are in a 

 state of irritability. They are contracted by a reflex 

 action that starts from the inflamed articulation, and 

 since the adductor muscles are supplied almost solely 

 by the obturator nerve, it is not unreasonable to 

 expect them to be especially disturbed if the 

 large share that the obturator nerve takes in the 

 supply of the hip be borne in mind. The adductors 

 are also rotators outwards, but this latter movement 

 would be resisted by the strong outer limb of the Y 

 ligament, as well as by the ligamentum teres, both of 

 which are rendered tense by rotation outwards during 

 flexion. The whole matter, however, requires further 

 investigation. 



5. Apparent shortening of the limb is due to 

 tilting up of the pelvis on the diseased side, and 

 bears the same relation to adduction that apparent 



