Dear Dr. K: My husband cracks his knuckles constantly. Aside from the fact that I find it annoying, I’m also worried that it’s bad for him. Can knuckle-cracking lead to arthritis or other problems?

Dear Reader: That “popping” noise that irritates you so much when your husband cracks his knuckles may well be music to his ears. But for those who don’t crack their knuckles, the appeal can be hard to understand. And, like you, some of my patients (spouses of habitual knuckle-poppers) have wondered what causes the sound and whether it’s harmful.

I passed on your question to my colleague Dr. Robert Shmerling, an arthritis specialist. This is what he told me. The “pop” of a cracked knuckle is caused by bubbles bursting in the fluid that lubricates your tendons and joints, called synovial fluid.

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