Most animal legs
will have some knees.

Including birds,
including bees,

including dogs
like Pekinese,

including cats
like Siamese.

There’s also apes
like chimpanzees

and watery-mammal
manatees.

And most of them all
have kneecaps, two.

including us,
the gnu, the shrew,

and even frogs
have kneecaps too.

But NONE are found
on a kangaroo.

Pondering These Knees by Celia Berrell

https://www.realclearscience.com/blog/2019/04/02/four_fascinating_facts_about_kneecaps.html

http://kneesafe.com/fun-facts-animal-knees/