kneepan vs os sesamoideum

kneepan and os sesamoideum both are nouns.

Word	Noun	Adjective	Verb	Adverb
kneepan	Yes	No	No	No
os sesamoideum	Yes	No	No	No

As nouns, os sesamoideum is a hypernym of kneepan; that is, os sesamoideum is a word with a broader meaning than kneepan:

kneepan: a small flat triangular bone in front of the knee that protects the knee joint
os sesamoideum: any of several small round bones formed in a tendon where it passes over a joint

Other hypernyms of kneepan include sesamoid, sesamoid bone.

kneepan (noun)	os sesamoideum (noun)
a small flat triangular bone in front of the knee that protects the knee joint	any of several small round bones formed in a tendon where it passes over a joint