Why Do Knuckles Crack? And is it Safe?

Scientists aren’t entirely sure about this one, but they have a pretty good idea

Our adult son, a musician, is a self-described champion knuckle cracker. I’ve heard him do it many times and I wouldn’t bet against him. It’s quite a spectacle. So I asked him to record one round of the routine I’ve seen (and heard!) him do several times a day: [YouTube video].

“I do it mostly out of habit,” he said. “But sometimes it’s quite relieving, especially after or during anything that works the hands, like weightlifting or playing an instrument.”

My knuckle cracking is nowhere near as thorough or predictable. But it does relax my hands during long days glued to a keyboard. (The scientists say joints do feel looser after a good cracking.) For others, knuckle cracking can be a nervous habit, a way to release mental energy. Kids probably find the sound pretty interesting.

The pop we hear when knuckles or other joints crack involves gas bubbles within the fluid that lubricates joints. But exactly how that air makes noise is a bit, well, up in the air.