system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes your bones pop?

Please explain what that noise is when you crack your back, or pop your knuckles.
gpt
I'll probably be downvoted for saying the c-word but i am currently a student in chiropractic school, probably one of the better people to answer this question. In most all of your joints is something called synovial fluid. Like all fluid there are molecules of gas in there. Gas like Hydrogen, oxygen, nitrogen, etc. Most of these molecules are bound (H20) but there are also ions. The popping sound you hear is the release of gas from the synovial fluid. The term for when gas is released from a joint is called a cavitation.