Knuckle cracking causes arthritis: True/False?

If you’re like me and rate the sound of cracked knuckles as an irritation second only to nails on a blackboard then this common warning seems like poetic justice. Yet, in a further sign of the unfairness of nature, arthritic hands do not come about because of cracked knuckles.

Arthritis isn’t even associated with knuckle cracking: there just isn’t any evidence that the two are related. When you look under the bonnet of each phenomenon it’s easy to see why. Osteoarthritis is caused by loss of cartilage in the joints which leads to bone damage and joint swelling. The other kind of arthritis, rheumatoid arthritis, is caused by a faulty immune system leading to joint inflammation. The bone-crunching noise of a cracked knuckle certainly sounds like it’s damaging something crucial, and it definitely inflames tempers, so why not joints? Yet the ghastly noise doesn’t signal cartilage damage and doesn’t trigger inflammation.

The sound of a cracked knuckle comes from the creation and sudden collapse of gas bubbles inside the synovium, the liquid-filled capsule that protects and nourishes the joint. As the knuckle is pulled apart the pressure inside this capsule is lowered and gases which have been dissolved in the liquid spring out of solution and form bubbles, just as happens when you open a bottle of fizz. When the knuckle snaps back the capsule is compressed and the bubble bursts with a bang.

So we have two unrelated processes. Joint cracking is about the fluid in between the joints, not the cartilage or other parts of the joint that are involved in arthritis.

That doesn’t mean knuckle cracking is harmless. It can lead to loss of hand function. There is some justice after all — though if you ask me the crackers are getting off easy.

If you’ve been cracking your knuckles to your heart’s desire without thought of the consequences then consider your bubble burst. You won’t get arthritis, but you can still expect problems. And just watch out if you start cracking around me — or you may find a knuckle sandwich heading your way.

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