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

Katie Panteli

Writer

Katie, a Warwick Biomed graduate, works for a science-publishing house in London with some of the world's most respected scientific minds. She's most interested in human biology, anything and everything that makes us tick.

• Video by Greg Kawchuk and colleagues
• University of Alberta, Canada
• Originally published under a Creative Commons Licence (BY 4.0)
• Research published in PLOS One, April 2015