Why do your knuckles pop? - Eleanor Nelsen?

Your knuckles pop because air bubbles inside your joints are being squished out like toothpaste from a tube.

When you bend or twist your fingers, it’s like squeezing a soft bag of air, the joint is the bag, and the ligaments and tendons around it act like the sides of the bag. Inside that joint is fluid, which has tiny air bubbles mixed in. When you move your finger quickly, those air bubbles get squished out with a little pop.

Imagine you have a bottle filled with soda and some air bubbles. If you shake it up and then open it suddenly, the air bubbles rush out with a fizz. That's what happens in your knuckles, the air bubbles escape quickly, making that fun pop sound.

Sometimes people say their knuckles pop when they're nervous or excited, just like how some kids click their fingers when they’re thinking. It’s not magic, it’s just air and movement working together to make a little noise!