mortise joint vs ankle joint

mortise joint and ankle joint both are nouns.

Word	Noun	Adjective	Verb	Adverb
mortise joint	Yes	No	No	No
ankle joint	Yes	No	No	No

As nouns, mortise joint and ankle joint are synonyms defined as:

mortise joint and ankle joint: a gliding joint between the distal ends of the tibia and fibula and the proximal end of the talus

Other synonyms of mortise joint include ankle, articulatio talocruralis.

mortise joint (noun)	ankle joint (noun)
a joint made by inserting tenon on one piece into mortise holes in the other	a gliding joint between the distal ends of the tibia and fibula and the proximal end of the talus
a gliding joint between the distal ends of the tibia and fibula and the proximal end of the talus