People tend to be split right down the middle when it comes to the subject of knuckle cracking: they either love it, or the very idea of it sends them into an episode of the gross-outs. Which camp are you in?
 If you're a knuckle-cracker, raise your hand (unless you're too busy cracking it, heh).

Have you ever wondered why you're compelled to crack? Drumroll... according to Dr. Rachel Vreeman, assistant professor of pediatrics at Indiana University School of Medicine and co-author of Don't Cross Your Eyes...They'll Get Stuck That Way!: "There's not any hard science to explain why it's so addictive, but certainly people speculate it's one of these

activities that releases nervous energy."
Like tapping your pen, chewing gum, biting your nails--cracking knuckles a habit, even though you're not actually cracking anything: "That sound you hear is synovial fluid vapor cavities--or gas bubbles--in the fluid around your joints. With certain amounts of pressure you can make those bubbles burst," Vreeman says.
 And while studies have shown that knuckle-crackers are no more likely to get arthritis than anyone else, but they do up their chances of hand discomfort (like swelling, less hand strength, and finger or joint injuries). So it's probably a good idea to leave your digits alone.