bone spavin

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A condition in horses caused by the deposition of new bone in the hock joint and sometimes producing lameness.

from The Century Dictionary.

• noun In farriery, a disease of the bones at the hock-joint.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun spavin caused by a bony growth