Is it bad to crack your knuckles?

I always crack my knuckles.

Yes, cracking knuckles is a very bad habit. It will change the shape and position of your knuckles.

It's not as bad as people make it out to be. For starters, it's quite common for joints to crack on their own, a lot of the time without you even noticing. What happens is as your body moves and grows, nitrogen builds up in your joints. Well when you crack your knuckles, you're simply displacing that gas. If you do it a lot at a young age, when you're older, you'll generally have larger knuckles. There's nothing wrong with having large knuckles though. People say that doing it will cause you to have arthritis, this is true, but not as definite as people make it sound. You could crack your knuckles once a day your entire life and never get arthritis, but if you cracked your knuckles every 5 minutes you'd get arthritis. Basically, all you have to do is pace yourself. Oh and soki is wrong, it won't change the position of your knuckles, if anything, it actually makes your joints more limber (for a period of time) because the area the nitrogen takes up is more dispersed, thus giving your joints more area to move in, that's why athletes crack their joints before a critical moment (e.g. before going up to bat).