NAVICTTLAB JOINT DISEASE. 149 



Navicular Joint Disease. 



This disease is far more frequent than is usually 

 supposed, and many horses are ruined by it, the 

 lameness being generally referred to the shoulder or 

 to some other part not at all in fault. 



Behind and beneath the lower pastern-bone in 

 the heel of the horse, and behind and above the 

 heel of the coffin-bone, is a small bone called the 

 navicular, or shuttlebone. It is so placed as to 

 strengthen the union between the lower pastern and 

 coffin-bone, and to enable the flexor tendon which 

 passes over it, to be inserted into the bottom of the 

 coffin bone, to act with more advantage. It thus 

 forms a kind of joint with that tendon. There is a 

 great deal of weight thrown on this bone and from 

 this navicular bone on the tendon, and there is con- 

 siderable motion or play between them in the bend- 

 ing and extension of the pasterns. 



It is easy to conceive, that from sudden concus- 

 sion or from rapid and over-strained motion, and at 

 a time when, from rest and relaxation, the parts 

 have not adapted themselves to the violent motion 

 required, there may be excessive play between the 

 bone and tendon, and the delicate membrane which 

 covers the bone or the cartilage of the bone, may 

 become bruised, inflamed and injured or destroyed, 

 and that all the painful effects of an inflamed and 

 open joint may result, and the horse be incurably 

 lame. Numerous dissections have shown that this 

 joint thus formed by the tendon and bone, has been 



