hinge joint vs knuckle joint

hinge joint and knuckle joint both are nouns.

Word	Noun	Adjective	Verb	Adverb
hinge joint	Yes	No	No	No
knuckle joint	Yes	No	No	No

As nouns, hinge joint and knuckle joint are synonyms defined as:

hinge joint and knuckle joint: a joint allowing movement in one plane only

hinge joint (noun)	knuckle joint (noun)
a joint allowing movement in one plane only	a joint allowing movement in one plane only
a freely moving joint in which the bones are so articulated as to allow extensive movement in one plane	a joint of a finger when the fist is closed