8 August, 1907. 



Lanuinss in Horses. 



471 



stifle against a door-post or other solid object, as when passing through 

 a stable door or colliding with trees on timbered pasture. 



On account of the shape of the lower end of the thigh bone {femur) 

 over which the patella plavs it is almost impossible for the dislocation to 

 occur in an inward direction. The bone is displaced outwards and may 

 be seen and felt as a prominence behind and to the side of its usual 



Fig. 72. Reprint of Mayhew's illustration of the attitude in dislocaticn of patella. 



position. Comparison with the normal stifle of the other limb or of 

 another horse will make the displacement more obvious. 



Symptoms. — My observation of the potsition of the limb when at rest 

 and the action during progression when this condition exists is somewhat 

 at variance with the usual written description in text-books and at all 

 events at variance with the impression given by any drawings I have seen. 

 It is stated for instance that " the affected limb is kept pointed to the 

 rear, straight and stiff " {Hayes) or " the limb becomes stretched back- 

 wards " {Williams), and this imaginary position of the limb is depicted 

 in Mayhew's illustration, of which Fig. 72 is a copy given for the purpose 

 of comparison with Figs. 73 and 74, which are reproduced from instan- 

 taneous photographs of a case which T had some years ago. Fig. 73 repre- 



Fig. 73. Dislocation of patella — position 

 at rest. 



Fig. 74. Dislocation of patella- 

 position during progression. 



sents the iposition of the limb when at rest. The fetlock is bent completely 

 over and the foot rests pendulous on the front of the wall on the ground, the 

 anterior border of the limb from the point of the hip to the hock being 

 almost in a straight line. The whole limb is apparently lengthened, the 

 fetlock and hock being lower than their fellows. Fig. 74 represents the 

 action during progression. The foot is swung from the hip outwards, 

 and is dragged forward until it leaves the ground, when it is jerked up 

 towards the fore leg. It appears rigid and straight, the hock and stifle 

 taking little part in the action. The photograph was taken just at that 

 moment when the limb was advanced furthest forward. 



