DISEASES OF THE HIND LIMB 



175 



It is very seldom necessary to giye fractures of tlie ileiun 

 any special care. If the animal is yery lame, it should l)e given 

 a narrow stall, and placed in a sling until it can support its 

 weight on the limb. The same treatment is indicated in cattle. 

 It is not adyisable to breed a mare that has had the ileum frac- 

 tured. The bony enlargement that results from the union of the 

 broken ends of the bone may interfere with the passage of the 

 foetus through the pelyic cayity and cause difficult parturition. 



Luxation of the Patella, " Stifle Out." — This is a common 

 accident in horses and mules. 

 Young, immature animals are 

 more prone to displacement of 

 the patella than when mature. 

 The displacement is usually up- 

 ward or outward. Outward dis- 

 placement is comparatiyely rare. 



The causes of "stifle out " 

 may be described as follows: 

 The patella or knee-cap rests on 

 a pulley-like articular surface 

 belonging to the inferior ex- 

 tremity of the thigh-bone. The 

 external lip of this articular surT 

 face is smaller than the internal 

 lip. The patella is held in place from aboye by the heayy 

 muscles of the anterior region of the thigh, and from below, by 

 straight ligaments that attach it to the leg-bone. If the retaining 

 structures mentioned become relaxed, the patella may, when 

 the limb is extended, become so displaced as to rest on the 

 superior portion of the external lip. Laxness of the muscles and 

 ligaments in young animals is a predisposing factor. Hard 

 work that tires the muscles and causes them to become relaxed, 

 strains, unusual moyements, as kicking in the stable and slip- 

 ping, may cause this accident. Congenital displacement results 



Fig. 44. 



Atrophy of the muscles of the 

 quarter. 



