The horse leg part between the fetlock and the stifle.
The hock is the complex joint between the fetlock and the stifle on the hind leg. It joins together the cannon bone to all the parts of the leg directly below the stifle. It is an obvious joint because of the point of the hock which is the part that sticks out obviously at the back. In a person the hock joint is the equivalent of the ankle. However because horses walk by standing on ‘tiptoes’, the hock joint is found quite high up on the leg.
So the hock joint is composed of the long bone that connects it to the stifle (tibia), the big bone that makes the point of the hock (tibiotarsal bone) and the cannon bone and many smaller bones that fill in the gaps between these three bones.
The hock is important because it quite often goes wrong. Much lameness of the hind legs is caused by the hock when it gets a bit worn and stiff. Disease or arthritis of the hock joint is called Bone Spavin. Bone spavin happens when all the many small joint parts of the hock get weak and start to disintegrate. New bone may be laid down causing spurs which rub on other parts of the hock. Hock arthritis (Bone Spavin) either starts because too much pressure is being put on the joint (maybe because of natural confirmation abnormalities like cow hocks) or because the bones are not strong enough because of mineral imbalance. The whole problem is easily treatable by your vet if approached in the right way.
A hock becomes ’capped’ when the point of the hock (the bit that sticks out) is damaged and the sack of fluid that exists at this point becomes distended and sore.