fetlock vs fetlock joint

fetlock and fetlock joint both are nouns.

Word	Noun	Adjective	Verb	Adverb
fetlock	Yes	No	No	No
fetlock joint	Yes	No	No	No

As nouns, fetlock and fetlock joint are synonyms defined as:

fetlock and fetlock joint: the joint between the cannon bone and the pastern

fetlock (noun)	fetlock joint (noun)
projection behind and above a horse's hoof	the joint between the cannon bone and the pastern
the joint between the cannon bone and the pastern