92 THE SURGICAL ANATOMY OF THE HORSE 



LUXATION OF THE HIP JOINT 



A reference to the description of the joint will recall the fact that 

 the articular head of the femur is kept in the cotyloid cavity by the 

 ligamentum teres. This is a very short ligament, its length being 

 sufficient only to allow the articular head to rotate freely whilst within 

 the cavity. It will be evident, therefore, that before luxation can occur, 

 the ligamentum teres must be ruptured. This rupture, then, is a constant 

 accompaniment of luxation. 



Falke (quoted by Moller) performed experiments on the dead subject 

 which proved that dislocation could occur without injury to the bones 

 or their articular surfaces. 



The disposition of the capsular ligament renders it necessary that 

 this ligament must be ruptured. But rupture of the pubio-femoral 

 ligament need not necessarily occur, since this ligament is inserted only 

 into the sulcus in the head of the femur and has no attachment to the 

 cotyloid cavity. 



Luxation may be due to a variety of causes and the symptoms 

 presented vary with the cause. 



Abnormal abduction at the hip is most likely to rupture the liga- 

 ments, particularly the ligamentum teres ; but some very violent 

 movement of the joint is necessary to produce luxation. 



When luxation occurs the animal is unable to place any weight upon 

 the limb, and the limb is therefore " carried." Manipulation will reveal 

 a loss of mobility in the joint. Some movements may be more easily 

 carried out, whilst others are completely restricted, the particular 

 movements depending upon the position taken up by the head of the 

 femur after dislocation. If the head is displaced in the downward 

 direction there will be a depression over the joint, whilst an elevation 

 will be present if the head has moved upwardly, in which case the limb 



