How true is the claim? It's not. The most common form of arthritis, an inflammation inside the joints, is osteoarthritis, which affects 21 million Americans. It's caused by such factors as genetics, obesity, and a history of sports injuries.

Why it gets repeated: The cracking sound makes some people shudder, and it makes sense to think that popping joints would lead to joint problems. In fact, while cracking won't lead to arthritis, it isn't smart. By pulling on your fingers, you create tiny nitrogen bubbles in the joints. The bubbles then burst, making the popping sound. People who push down on their knuckles are snapping their tendons over bony spots. Both of these, done repetitively, can irritate the tendons.

Bottom line: You won't bring on arthritis with knuckle cracking, but kicking the habit may still help you avoid achy hands.