pelvic arch vs hip joint

pelvic arch and hip joint both are nouns.

Word	Noun	Adjective	Verb	Adverb
pelvic arch	Yes	No	No	No
hip joint	Yes	No	No	No

pelvic arch (noun)	hip joint (noun)
the structure of the vertebrate skeleton supporting the lower limbs in humans and the hind limbs or corresponding parts in other vertebrates	the ball-and-socket joint between the head of the femur and the acetabulum