What's wrong with my knee?

Every time I squat to sit down, my knee crackles and then when I get up, it pops. I don't really mind the popping noise, but the crackling really makes me cringe. It sounds terrible. It doesn't really hurt but the noises bother me. I feel like me knee cap is like breaking apart or something. I try to get up in different ways to avoid my knee from cracking because I hate it so much. I'm only 13 so I'm kind of young to be having knee problems.