knee joint vs human knee

knee joint and human knee both are nouns.

Word	Noun	Adjective	Verb	Adverb
knee joint	Yes	No	No	No
human knee	Yes	No	No	No

As nouns, knee joint and human knee are synonyms defined as:

knee joint and human knee: hinge joint in the human leg connecting the tibia and fibula with the femur and protected in front by the patella

Other synonyms of knee joint include articulatio genus, genu, knee.

knee joint (noun)	human knee (noun)
hinge joint in the human leg connecting the tibia and fibula with the femur and protected in front by the patella	hinge joint in the human leg connecting the tibia and fibula with the femur and protected in front by the patella