Bog-spavin in horses can be thought of as ’windgalls in the hock’. Bog-spavin is first seen as a swelling in two distinct locations at the back and front of the hock joint. These swellings are where the joint fluid of the top joint of the hock has increased in the sack in which it is contained and pushes out so it becomes visible.
Bog-Spavin normally occurs in horses that have poor conformation and does not cause too much of a problem. The poor conformation of the joints causes extra fluid to be produced which perhaps makes the joint less liable to get damaged.