ankle joint vs mortise joint

ankle joint and mortise joint both are nouns.

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

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

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

Other synonyms of ankle joint include ankle, articulatio talocruralis.

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