system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Whats cracking when i crack my knuckles?

Or toes or back or any other joint that you "crack"? What's actually happening in the joint?
gpt
A lubricant is found in your joints, called synoval fluid. When you crack your knuckles, you reduce the pressure on the fluid and gas bubbles (nitrogen, oxygen, CO2) burst.

It takes about 20 minutes for the gas to dissolve back into the fluid, that's why you can only crack your knuckles every 20-30 minutes.