In a way, yes because you are breaking the tissue in between your bones every time you crack your knuckles. And in my opinion, it's just not healthy to crack any joint everyday. Good luck. EDIT: I don't mean "break" per say, but every time you crack your knuckles you "loosen" your tissue between the joints and bones.
I heard about it and I don't know whether to believe it or not but i do it anyway. And if I get arthritis when I'm older....well then who cares, lots of old people get arthritis anyway and it doesn't effect you much.