Is cracking your knuckles bad for you?

Although Mom was probably right about a lot of things, here’s one time when she might have led you astray. Contrary to popular belief, cracking your knuckles doesn’t cause arthritis or give you knobby knuckles.

It’s an annoying habit, but there are no biological consequences. You won’t need new joints and your joints won’t get bigger from cracking your knuckles.

So, what happens when you crack your knuckles? Negative pressure in the fluid surrounding the joint keeps the bones from slipping out of place. When you press on the knuckle, you create a low-pressure area within the fluid. This pressure change draws carbon dioxide (CO2) into a bubble that breaks almost instantly, making the popping noise. Once that gas bubble has popped, it takes a while for another bit of CO2 to dissolve into the low-pressure area, which is why you can’t crack the same knuckle repeatedly in rapid succession.
All of this is somewhat theoretical, but this is the best guess of how it happens.

Because knuckle cracking isn’t a big problem — and research looking into it is both invasive and expensive — little scientific attention has been paid to it, says Dr. David Steinberg, assistant professor in the department of orthopedic surgery at the University of Pennsylvania Medical Center in Philadelphia. “If we could demonstrate that it causes a problem, then maybe there’d be grant money out there to support further investigation,” says the confessed knuckle-cracker of 15 years.

Furthermore, if there were an association between knuckle cracking and arthritis, doctors would certainly be seeing a lot more arthritis.

But before you launch yourself into a knuckle-cracking frenzy, be warned that vigorous knuckle cracking may not be trouble-free — it can cause wear and tear on the joints. For example you can stretch a ligament so much that it loses its stability. Ligaments normally have a little elasticity and a small amount of stretch.

So what should you do if you’re a knuckle cracker and you’re worried about your joints? One of my instructors told me, ‘If a joint pops but it doesn’t hurt, don’t worry about it. If it hurts then you might not want to do that anymore.’

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