system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is that clicking sound your arms and shoulders do when you wake up?

Especially the shoulders and neck, they do these clicking noises that are different from the "bones sound" you make when you "crack your fingers". It sounds more like coming from nerves and muscles. After a few movements, you can't feel it anymore. Why is that?

Edit: it's more like a "muscles" (or nerves, I suppose) noise rather than bones.
gpt
Not an expert or anything, but its basically some gasses that build up inside your joints in-between your bones. When you crack your fingers/neck/back, etc. The gasses are being pushed outside and because everything is so tight it the bubbles just pop and make the cracking sound.

No worries to granma stories where you get arthritis if you crack your joints, its been tested and there are zero connections between cracking your finger/joints and getting arthritis.