Cracking your knuckles sounds like something terrible is happening in there, but no, your bones are not breaking or banging against each other. What happens is that, when the joint is stretched, the pressure of the synovial fluid changes, which is what helps lubricate it, and small gas cavities form.
That “crack” that so many people love, and others can’t stand, comes from that. That’s also why you can’t crack the same finger twice in a row: the area needs a few minutes for those gases to dissolve again before it can make the sound again.
And no, doing it doesn’t mean you’re headed straight for arthritis, as many of us grew up hearing. Science has not found a clear relationship between cracking your knuckles and developing arthritis in your hands. That said, if it hurts, swells, or leaves lingering discomfort, then it’s no longer a simple habit: it’s better to get it checked out.
Watch the video that explains it: