THOROUGHPIN
Noun
thoroughpin (plural thoroughpins)
An abnormal swelling (tenosynovitis) on the sides of the hock joint of horses
Source: Wiktionary
Thor"ough*pin`, n. (Far.)
Definition: A disease of the hock (sometimes of the knee) of a horse,
caused by inflammation of the synovial membrane and a consequent
excessive secretion of the synovial fluid; -- probably so called
because there is usually an oval swelling on each side of the leg,
appearing somewhat as if a pin had been thrust through.
Source: Webster’s Unabridged Dictionary 1913 Edition