The original fact on cracking your knuckles is one of our most popular of all time. Basically, it said that cracking your knuckles is not bad for you, no matter what the old wives' tales may say.
However, probably the most convincing study on this comes from a man who just won an "Ig Nobel" for his self-study on knuckle-cracking.
Dr. Donald Unger has spent the better part of the last 60 years cracking the knucles of his left hand. He started because he wanted to prove his mom wrong when she told him he would have health problems if he kept doing it.
Since he started, he has NEVER cracked the knuckles on his right hand. This means that, if it's true that cracking your knuckles was bad for your fingers, then his left-hand fingers would have a horrible arthritis while his right-hand fingers would be ok.
Well, the doctor, now 83, says "there is not the slightest sign of arthritis in either hand." His research has won him an "Ig Nobel," which is a tongue-in-cheek parody of the real Nobel awards.
I'm glad he did this, because I don't know if I'd have the willpower to resist NOT cracking my other hand's knuckles if I could only do one side.