A bony outgrowth on the inner and lower part of the hock is termed a bone-spavin (fig. 324).

The enlargement usually appears towards the front, but it may occupy a backward position, or extend from front to back. Spavins vary in size as well as in position. Sometimes they are small and with difficulty identified, at others they reach a considerable size. The same variation appears in respect to form. They may present themselves as rounded, or more or less pointed and irregular swellings, or as a projecting ridge, extending across the hock from back to front. Usually they appear on one hock only, but frequently both are affected either simultaneously or consecutively. Hocks of every variety of size and conformation, from the biggest and best to the smallest and weakest, are liable to become affected, but it goes without saying that the disease is most frequently found in the latter.

Causes

The predisposition to spavin is unquestionably hereditary. Horses with straight quarters and upright pasterns seem especially liable to it. Sprain and concussion to the joint, acting separately or together, are the exciting causes, and there is reason to think that these accidents are more especially likely to occur when animals are forced in their work under circumstances of fatigue and want of condition and development. The outward enlargement is an evidence of the inflammation going on in the articular surfaces of the bones.

The great variation found to exist in the conformation of the hocks of different horses, and indeed sometimes in the two hocks of the same horse, has ever been a stumbling-block to the veterinarian in the diagnosis of spavin, and a mine of wealth to lawyers and learned counsel. Coarseness or lumpiness is a recognized condition of normal development in the hocks of some horses, and to distinguish between the natural irregularities of coarseness and those resulting from disease is always difficult and sometimes impossible. If these facts were more generally recognized and allowed by veterinary practitioners, much of the litigation which now engages our law-courts would be avoided, and the veterinary profession would be saved from those strange exhibitions of discrepancy which tend to weaken public confidence in their opinion and advice, if they do not engender distrust.

Bone Spavin. a, Spavin.

Fig. 324. - Bone-Spavin. a, Spavin.

Symptoms

The immediate effect of the jar or sprain giving rise to spavin is to produce lameness, sometimes slight, sometimes severe. This may or may not pass away, to return again when the enlargement of the hock appears and encroaches upon the connecting ligaments of the joint. The action of the spavined horse is marked by stiffness of the affected limb. In movement the hock is imperfectly flexed and the leg has the appearance of being carried.

Compared with the opposite limb the stride is short and limping, and the quarter is noticed to drop when the foot is brought to the ground. If continued in work the toe strikes the ground and in time becomes worn. Spavin lameness is most severe after a rest, and particularly noticeable when the horse first leaves the stable, but it improves as he goes on. Heat may or may not be detectable in the joint, and as the patient stands the limb is rested on the toe or front part of the foot.

Treatment

On the first appearance of the disease the animal should cease to work and receive a dose of physic. At the same time fomentations or hot bandages should be applied to the hock until the existing inflammatory action is subdued.

Cold-water irrigation for a few days should follow, after which a repetition of blisters at intervals of a fortnight or three weeks may suffice to effect a cure. Should, however, the lameness still continue, choice must be made between the operations of firing and setoning, in either of which case a long rest at grass will be desirable.

Horses with spavins are frequently restored to service and continue to work without interruption for the rest of their lives. Others, however, are permanently crippled. The latter result is most frequent when the spavin occupies a forward position.