If you love making your knuckles and other joints pop, you might’ve heard that doing so is “bad for you” and that “you’ll get arthritis.” Short answer: we’re not sure. Long answer: this video from Vox gives you the lowdown on what’s actually happening in your joints.
That characteristic (and honestly, disturbing) popping sound you hear when you crack knuckles is from a gas-filled lubricant within your joints called synovial fluid. Popping your joints creates stretched out space between your bones and sucks the fluid into that space, the event of which is associated with that lovely sound.
As for whether it’s “bad,” well, the research is not clear. If you don’t feel pain when you crack them, then you probably don’t need to worry.
Here’s what happens to your knuckles when you crack them | Vox
via Lifehacker
Why Your Knuckles Make That Popping Sound When You Crack Them