Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: turnipsock on 17/06/2008 13:01:44
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Does cracking your knuckles lead to arthritis?
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I can crack all the joints in my hand except one, its a good party trick as I ask somebody to pick a joint and then I crack it, but I often get told that I will get arthritis, is this true?
The only joint I can't crack is the metacarpophalangeal joint in my thumbs, but I can do this...
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Nice hands...do you moisturise? ;-)
Bud rang in to ask, "What happens when you crack your joints, and is it bad for you?"
Some scientists wanted to learn more about knuckle cracking, so they actually stuck a sensitive microphone onto a finger. They found that there wasn't just one single sound when you cracked a finger joint - there were actually two separate sounds. The joint space is the space between the bones. There is a liquid in this space, and there are ligaments on each side, holding the bones together. As you pull on the joint, you first drop the pressure in the joint space - and the ligaments get sucked in. Once this pressure gets low enough, a bubble pops into existence - making a popping sound, which is the first of the two sounds.
Now this bubble has a certain size - on average, about 15% of the now-bigger joint space. Because the joint space suddenly has a bubble in it, the liquid, just as suddenly, pushes on the ligaments - snapping them back to their original position. This snapping back of the ligaments is the second sound.
The energy set loose inside the joint is only about 7% of what you need to damage the cartilage. But if you crack your knuckles often enough, you can end up with swollen ligaments.
Another study looked at 300 people who had been cracking knuckle joints for 35 years. They had slightly swollen joints (which is no big deal). But the real surprise was that their hands were weaker - their grip strength was one quarter as strong as it should been!
So cracking your knuckles won't bother you in the short term, but 35 years from now, you might not be able to open a jar of Vegemite!
more on knuckles...
References
Jearl Walker, The Flying Circus of Physics, by Jearl Walker, ISBN 0-471-02984-x, 1975, p. 226. Jorge Castellanos & David Axelrod, 'Effect of habitual knuckle cracking on hand function', Annals of Rheumatic Diseases, Vol. 49, 1990, pp. 308-309.
Sam W. Wiesel, M.D. etal, 'Occipitoatlantal Hypermobility', Spine, Vol. 4, May/June 1979, pp. 187-189.
John F. Rothrock, M.D., 'Vertebral artery occlusion and stroke from cervical self-manipulation', Neurology, October 1991, p. 1696. Raymond Brodeur, D.C., Ph.D., 'The Audible Release Associated with Joint Manipulation', Journal of Manipulative and Physiological Therapeutics, Vol. 18, No. 3, March/April, 1995, pp. 155-164.
© Karl S. Kruszelnicki Pty Ltd 2003.
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Interesting... I usually sound like a bowl of rice crispies when I do my first lot of stretching exercises of a day, and from my jaw right down to some on the bones in my feet. The oudest cracks seem to come from my neck, elbows, shoulders and ankles, but if I rest my hand over a knee joint and flex that under it, although I cannot hear it, I can certainly feel it creaking and grating!
Alas, I am a worn out wreck! lol
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Well, There's this story "Regardless of the theories, there is little evidence that knuckle cracking causes arthritis: a survey of knuckle crackers showed no more incidence of arthritis than non-knuckle crackers.
One American doctor went so far as to crack the knuckles on just one hand for 50 years to see if there was a difference between that hand and the other - there wasn't."
from here
http://www.newscientist.com/backpage.ns?id=mg19726462.600
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Were factors other than grip strength tested though? For example what if the muscle near the joints became more flexible, although weaker? You will get differences in the type of muscle tissue depending on their use, like a weightlifter will have strong, but short-term burst type of muscle, where a rower will have long term endurance muscle but would have a lot of trouble lifting heavy weights.