The pop when you crack your knuckles is not your bones. It comes from the fluid between them.
What makes the pop?
Inside each finger joint is a small pocket of slippery fluid. When you pull or bend the joint, the space inside suddenly gets bigger. A gas bubble suddenly forms in the fluid, and that bubble makes the pop.
Why not again right away?
The bubble stays for a while, so the same knuckle will not crack again right away. It takes around 20 minutes before it is ready again.
Does it cause arthritis?
Many people worry that cracking your knuckles causes arthritis. One doctor tested it by cracking the knuckles of only one hand for over 50 years. Neither hand got arthritis, and bigger studies found no link, either.
