362 



HEALTH AND DISEASE 



system. At the same time it is to be observed that the displaced skin of 

 the knee forming the wall of the abscess must be bound down by means 

 of a bandage, as previously suggested, and the horse kept in the standing 

 posture. 



CAPPED HOCK 



When an enlargement appears on the point of the hock, the part is said 

 to be "capped" (fig. 386). There are two conditions to which this term is 

 applied one involving the skin and tissue 

 beneath it, and the other the synovial 

 membrane interposed between the bone 

 (calcis) and the tendon passing over it. 



A short description of the anatomy 

 of this part will render this difference 

 intelligible. The point of the hock 

 comprises a bony prominence, over 

 which is spread an expanded portion 

 of the tendon of the gastrocnemius in- 

 ternus muscle, and in order that the 

 latter may more freely move over the 

 former, a synovial sac is interposed be- 

 tween the two and supplies the necessary 

 fluid to lubricate the apposed surfaces. 

 On the posterior aspect of the tendon 

 there is a considerable quantity of 

 cellular tissue, which by its looseness 

 enables the skin to move freely over 

 the point of the hock, and thus to 



accommodate itself to the extremes of flexion and extension during 

 progression. 



Injury to this cellular structure results in inflammation (cellulitis) and 

 swelling, which, when attended with an accumulation of fluid in the part, 

 constitutes a serous abscess. 



The other form of the disease is always one of distension of the synovial 

 sac with synovial secretion; but inasmuch as it does not concern the 

 summit of the hock, but only appears at the sides, the term " capped 

 hock " ought never to have been applied to it. 



Causes. Whether the enlargement be of one description or the other, 

 it is invariably the result of external violence. The most common cause is 

 injury done to the point of the hock in lying down on a badly littered floor, 

 or by slipping and striking the part in the act of rising. Pitching on the 



Fig. 386. Capped Hock 



