This section is from the book "The Farmers Ready Reference Or Hand Book Of Diseases Of Horses And Cattle", by S. C. Orr. . Also available from Amazon: The Farmer's Ready Reference;.
A bone spavin is a bony enlargement on the inner part of the hock joint. There are several things to be taken into consideration before deciding as to the curability of a bone spavin. If the enlargement is low down, not of long standing and only lame at starting and ceasing after becoming warmed up, the prospect to cure it is favorable. But if it is located high up, involving the entire joint, or is of very long standing and the horse old, or if the lameness does not grow less after being warmed up, then there is little prospect of making a cure.
Symptoms. - If the enlargement is of good size it can be plainly seen. In trotting there will be dropping of the hip, and the step on the lame side will be shorter than on the other; if the animal is working let it stand for several hours and then start off lively; there will be lameness, probably touching the toe first then easing down on the foot and after going a short distance the lameness will almost or entirely disappear. When standing the foot is rested forward of the other, and sometimes with the heel resting against it. There is not much soreness or pressure
Treatment. - If taken in the beginning, sometimes complete rest in the stable with a biniodide of mercury blister applied once in three weeks for several applications will cure it; but few confirmed cases of bone spavin can be cured short of the free use of the firing iron in the hands of an expert. In either the blister or the use of the firing iron the horse should remain in the stable for the first month and then have at least two more months to run idle before putting to work.