This disease is of an entirely different nature from that referred to in the section on "Diseases of the Organs of Locomotion". It is presented by a soft fluctuating enlargement at the upper and inner part of the hock-joint, arising out of distension of the capsule (fig. 363) of the true hock-joint with synovia or "joint oil".
It most commonly occurs in young horses between one and three years old. The heavy breeds are especially liable to it, and most so animals of lymphatic temperament, with round fleshy legs, coarse hair, thick skin, and feeble energy.
The predisposition to bog-spavin is essentially hereditary. It-may also be acquired by causes which induce poverty and weakness. Young colts of rapid growth when badly nurtured readily contract the disease. The exciting causes are overwork while young, and sprains to the joint; but large numbers of cases are induced by the pernicious system of forcing, which young stock undergo during their show-yard career, and we have known many fine specimens of the heavy breeds to have been hopelessly ruined in their infancy by this practice.
Bog-spavin may arise suddenly, or it may appear in a slow and progressive manner. The former is mostly the case when the result of sprain, and also as a consequence of high feeding and confinement. Work and wear lead to a more gradual and often a more abiding enlargement of the joint. Where the disease is sudden in its onset, it is usually attended with pain and lameness, and the joint is hot, tense, and painful to pressure.
Fig. 363. - Bog-Spavin B, The distended joint with the skin removed.
The amount of swelling varies in different cases, sometimes it is very considerable, in which case it is not confined to the front of the joint, but is also seen on either side near to the seat of thorough-pin, for which it is often mistaken. It must be pointed out that the lameness is not always in proportion to the size of the swelling. Very large bog-spavins are sometimes found to occasion but slight defect in action, while smaller ones may be attended with severe lameness.
In this disorder the object of treatment will be - 1, to subdue inflammation; 2, to promote absorption of the fluid existing in the capsule of the joint; 3, to prevent excess of secretion; and 4, to bring about contraction of the overstretched and enlarged joint capsule. Where the disease is attended with inflammatory symptoms, or is brought about by dietetic causes, a dose of physic should be promptly administered and the animal put on a bran diet. Hot fomentations to the part, or what is equally beneficial, douching the joint with cold water for half an hour to an hour three times a day, will be necessary. Should the latter course be adopted, cold-water bandages must be applied to the part in the intervals and frequently changed.
After the inflammatory action has been subdued a blister should be applied over the entire surface of the hock, and repeated if necessary two or three times at intervals of three to four weeks.
In the more chronic cases, firing, and blistering-over the fired surface, will require to be resorted to. Iodide of potassium, given in doses of 2 to 3 drams morning and evening, will assist in the reduction of the swelling. Where poverty exists a liberal ration of good food should be allowed, together with iron tonics.
Animals suffering from bog-spavin are benefited by a run at grass after the inflammation has been reduced, and in some cases the absorption of the fluid may be hastened by the application of a suitable compress to the affected joint (fig. 364).