Cracking your knuckles causes arthritis.

If cracking your knuckles caused arthritis, half the planet would be gnarled and creaking. The sound comes from tiny gas bubbles popping in your joints — not your skeleton crumbling like old IKEA furniture. Studies show zero link to arthritis, though your friends may still glare at you for doing it. So go ahead and crack, but maybe don’t do it during job interviews.