Why do bones "pop"?

I got to wondering the other day... why do things like our elbows, knees, neck, fingers, ankle, and back pop sometimes? How can people continuously crack their knuckles? When a certain part pops, does it mean you have a problem?

*Thanks,
lifeoftheparty20

Popping your bones isn't nothing to serious, but it can cause long term, if not permanent injury.

The cracking noise in your bones is infact carbon dioxide bubbles popping in the cartilage between the joints. If you crack your bones continuously, it can leads to problems such as arthiritus.

that exacly what I was told that I can lead 2 arthiritus and that what I say 2 my friends when they "try 2 show off" that they can click their necks and arms and knuckles lol then they complain that their necks are sore afterwords dum bunch of kids

Actually, if you look it up on the internet, for example, on howstuffworks.com, it says there have been studies that have shown that popping your knuckles and stuff is not actually related to arthritis. It does say, however, that your grip will probably not be as strong.