Bog spavin is more of a clinical sign that something is wrong, rather than an diagnosed condition. It is a soft, fluid-filled swelling on the horse's tibiotarsal or tarsocrural joint in the hock. It appears at the front towards the inside and on the outside just below and infront of the point of the hock. It may appear on one or both hind legs. Horses with bog spavin may or may not be lame.

The swelling is caused by inflammation of the joint lining, which results in an increase in the fluid inside the joint. Bog spavin is often confused with bone spavin and throughpin. The difference between bog spavin and bone spavin is that with bone spavin, it is a firm swelling which appears in the lower joints of the hock and is caused by osteoarthritis. In the case of thoroughpin, the swelling occurs at the back of the horse's hind leg, just above the point-of-hock.

Bog spavin can develop in horses due to conformation (Horses with post legs, sickle hocks, and straight hock conformation predisposes them to developing bog spavin), osteoarthritis, osteochondrosis (OCD), infection, certain vitamin/mineral deficiencies, or trauma. The most common vitamin/mineral deficiencies associated with the development of bog spavin are vitamin A, vitamin D, calcium, and phosphorus.

Treatment for Bog Spavin

Treatment of bog spavin depends on the underlying cause. Not all horses with bog spavin require treatment.