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26 April 2015

Finger Clicking Good?

Many people can ‘crack’ or ‘click’ their joints but the science behind the sound – so irritating to some of us – had never been elucidated. Now researchers have used cine MRI [moving scans] to visualise knuckle cracking. By pulling on a finger, the joint surfaces were seen to separate suddenly, and as there isn’t enough fluid to fill up the increased space, air gathers within the synovial cavity. This air-filled space is created at the same time as we hear the ‘crack’ and the whole process (seen here) happens in about 300 milliseconds [the blink of an eye]. But this bubble of air doesn’t burst as previously thought; instead, it persists and gradually disappears. Continually cracking your joints was said to play a part in joint degeneration, but so far this hasn’t been shown. Cracking your knuckles may even have therapeutic benefits – although not necessarily for those in earshot.

Written by Katie Panteli

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BPoD stands for Biomedical Picture of the Day. Managed by the MRC Laboratory of Medical Sciences until Jul 2023, it is now run independently by a dedicated team of scientists and writers. The website aims to engage everyone, young and old, in the wonders of biology, and its influence on medicine. The ever-growing archive of more than 4000 research images documents over a decade of progress. Explore the collection and see what you discover. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.

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