DISEASES OF JOINTS. 333 



Cause. — The great, comprehensive, common cause of, sometimes 

 permanent, sometimes only transient, disability of the horse is exter- 

 nal traumatism. 



Blows, bruises, hurts by nearly every known form of violence, 

 falls, kicks, lacerations, punctures — we may add compulsory speed 

 in racing and cruel overloading of draft animals — cover the entire 

 ground of causation of the diseases and injuries of the joints now 

 receiving our consideration. 



In one case, a working horse making a misstep stumbles, and fall- 

 ing on his knees receives a hurt, variously severe, from a mere abra- 

 sion of the skin to a laceration, a division of the tegument, a slough, 

 mortification, and the escape of the synovial fluid, with or without 

 exposure of the bones and their articular cartilages. 



In another case, an animal, from one cause or another, perhaps an 

 impatient temper, has formed the habit of striking or pawing his 

 manger with his fore feet until inflammation of the kneejoint is 

 induced, first as a little swelling, diffused, painless ; then as a perios- 

 titis of the bones of the knee; later as bony deposits, then lameness, 

 and finally the implication of the joint, with all the various sequelae 

 of chronic inflammation of the kneejoint. 



In another case, a horse has received a blow with a fork from a 

 careless hostler on or near a joint, or has been kicked by a stable 

 companion, with the result of a punctured wound, at first mild- 

 looking, painless, apparently without inflammation, and not yet caus- 

 ing lameness, but which, in a few hours, or it may be only after a few 

 days, becomes excessively painful, grows worse, the entire joint swells, 

 presently discharges, and at last a case of suppurative synovitis is 

 jaresented^ with perhaps disease of the joint proper, and arthritis as 

 a climax. The symptoms of articular injuries vary not only in the 

 degrees of the hurt, but in the nature of the lesion. 



Or the condition of hroken knees., resulting as we have said, may 

 have for its starting point a mere abrasion of the skin — a scratch, 

 apparently, which disappears without a resulting scar. The injury 

 may, however, have been more severe, the blow heavier, the fall aggra- 

 vated by occurring upon an irregular surface, or sharp or rough ob- 

 ject, with tearing or cutting of the skin, and this laceration may re- 

 main. A more serious case than the first is now brought to our notice. 



Another time, immediately following the accident, or possibly as 

 a sequel of the traumatism, the tendinous sacs may be opened, with 

 the escape of the synovia ; or worse, the tendons which pass in front 

 of the knee are torn, the inflammation spreads, the joint and leg 

 are swollen, the animal is becoming very lame; synovitis has set in. 

 With this the danger becomes very great, for soon suppuration will be 

 established, then the external coat of the articulation proper becomes 

 ulcerated, if it is not already in that state, and we find ourselves in 



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