Knuckle cracking: scientists explain what's really going on
Is knuckle cracking bad for you? Scientists hope 'pull my finger' study will pave the way for answers
An international team of scientists claims to have solved the decades-long debate of what happens when people crack their knuckles.
Using MRI video, scientists found that the "popping" sound was caused by a gas-filled cavity forming rapidly within the fluid surrounding the joint.
A similar conclusion was drawn in a 1947 study, but research in 1971 claimed the noise was related to the bubble collapsing rather than forming.
Subscribe to The Week
Escape your echo chamber. Get the facts behind the news, plus analysis from multiple perspectives.
Sign up for The Week's Free Newsletters
From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.
From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.
"We call it the 'pull my finger study' – and actually pulled on someone's finger and filmed what happens in the MRI," said lead author Greg Kawchuk, a professor at the University of Alberta's Faculty of Rehabilitation Medicine. "When you do that, you can actually see very clearly what is happening inside the joints."
Kawchuk likened the process to forming a vacuum. "As the joint surfaces suddenly separate, there is no more fluid available to fill the increasing joint volume, so a cavity is created and that event is what's associated with the sound," he explained.
Canadian chiropractor Jerome Fryer, who can crack all of his fingers on demand, was used as a test subject, with his fingers inserted one at a time into a tube connected to a cable that was slowly pulled until the knuckle joint cracked.
The MRI video, which showed each 310-millisecond knuckle crack in real time, revealed a white flash just before the cracking. Kawchuk said the white flash, which had never been observed before, could be water suddenly drawn together.
The team hopes that the findings, published in scientific journal Plos One, will pave the way for new research into the benefits or dangers of knuckle cracking.
Previous studies provided conflicting results, with some saying habitual knuckle cracking does not appear to cause long-term harm and others showing that the force of knuckle cracking has enough energy to damage hard surfaces.
Kawchuk said future research on knuckle could also offer insight into other joints in the body, including the spine, and help explain why they become arthritic or injured.
Create an account with the same email registered to your subscription to unlock access.
Sign up for Today's Best Articles in your inbox
A free daily email with the biggest news stories of the day – and the best features from TheWeek.com
-
The pros and cons of globalization
Pros and Cons Globalization can promote economic prosperity but also be exploitative
By Justin Klawans, The Week US Published
-
Magazine solutions - October 11, 2024
Puzzles and Quizzes Issue - October 11, 2024
By The Week US Published
-
Magazine printables - October 11, 2024
Puzzles and Quizzes Issue - October 11, 2024
By The Week US Published
-
Neanderthal gene ‘caused up to a million Covid deaths’
Speed Read Genetic tweak found in one in six Britons means cells in the lungs are slower to launch defences
By The Week Staff Published
-
Legalising assisted dying: a complex, fraught and ‘necessary’ debate
Speed Read The Assisted Dying Bill – which would allow doctors to assist in the deaths of terminally ill patients – has relevance for ‘millions’
By The Week Staff Last updated
-
Vaccinating children: it’s decision time for the health secretary as kids return to school
Speed Read Sajid Javid readying NHS England to roll out jab for children over 12, amid fears infections will rocket
By The Week Staff Last updated
-
‘Vaccination blunts, but does not defeat’: exploring Israel’s fourth Covid wave
Speed Read Two months ago, face masks were consigned to bins. Now the country is in a ‘unique moment of epidemiological doubt’
By The Week Staff Published
-
Thousands told to self-isolate in Covid app pinging error, claims Whitehall whistleblower
Speed Read Source says Matt Hancock was privately told of the issue shortly before he resigned as health secretary
By The Week Staff Published
-
Record 5.45m people on NHS England waiting lists
Speed Read Health chief warns that crisis is nearing ‘boiling point’ as backlog grows
By The Week Staff Last updated
-
Covid testing: the ‘great new game of holiday roulette’
Speed Read On one day last week, the price of a private PCR test ranged from £23.99 to £575
By The Week Staff Published
-
San Marino is first European country to offer ‘vaccine vacation’
Speed Read Tiny landlocked nation to give Russian Sputnik vaccine to paying tourists
By The Week Staff Last updated