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I pop my knuckles fairly frequently, and I have been told on several occasions that doing so is bad for your joints. Is this true? Have there been any medical studies on this?

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This article mentions a study of 300 people that concluded that it wasn't, but I cannot find the actual study. –  fredley Mar 25 '11 at 18:10
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I've been a knuckle-cracker for 28 years, and I'm just fine. And believe me, I'm no genetic superman...unless superman is bald, 5'6", and 20 lbs overweight. –  ajax81 Mar 25 '11 at 20:41
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I'm pretty sured that you can be wacked by people around who are annoyed with the sound –  Dyppl Mar 26 '11 at 21:16
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@ajax81 Anecdotal evidence has rather no value. We are all very different. –  Joze Oct 21 '11 at 11:12
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@ajax81: clearly, your knuckle-cracking has caused the balding, medium height, and overweightness. What did you think they meant by bad for you? ;) –  Domenic Nov 8 '11 at 17:49

1 Answer 1

up vote 109 down vote accepted

It seems to me like the concern about the negative impact of knuckle cracking brought up in the literature is if it leads to arthritis. Which of course isn't the only harmful thing it could cause.

The Ig Nobel in medicine was in 2009 awarded to Donald L. Unger for research around this very thing. Unger cracked his left hand knuckle systematically for 60 years while leaving his right hand uncracked. Showing that in at least his case it didn't cause any harm. I believe he published his result here.

Beyond that there seem to be two larger studies. The first one published in the British Medical Journal titled Effect of habitual knuckle cracking on hand function shown that there is indeed some problems caused by cracking knuckles:

To investigate the relation of habitual knuckle cracking to hand function 300 consecutive patients aged 45 years or above and without evidence of neuromuscular, inflammatory, or malignant disease were evaluated for the presence of habitual knuckle cracking and hand arthritis/dysfunction. The age and sex distribution of the patients (74 habitual knuckle crackers, 226 non-knuckle crackers) was similar. There was no increased preponderance of arthritis of the hand in either group; however, habitual knuckle crackers were more likely to have hand swelling and lower grip strength. Habitual knuckle cracking was associated with manual labour, biting of the nails, smoking, and drinking alcohol. It is concluded that habitual knuckle cracking results in functional hand impairment.

The second one published in the western journal of medicine titled The Consequences of Habitual Knuckle Cracking examined 28 people in a Jewish home for the aged, with an x-ray. It finds no harm:

The data fail to support evidence that knuckle cracking leads to degenerative changes in the metacarpal phalangeal joints in old age. The chief morbid consequence of knuckle cracking would appear to be its annoying effect on the observer.

So it seems like the the answer is that there's some harm, but it's probably so negligible it's not worth worrying about.

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If anything is likely to cause a problem, it's got to be "cracking knuckles with an x-ray". So I guess we can consider the case closed. –  Chris Wuestefeld Mar 25 '11 at 19:38
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"habitual knuckle crackers were more likely to have hand swelling and lower grip strength" Correlation does not imply causation. Did they check that it's not the other way around? I only have one knuckle that wants to be cracked. –  endolith Mar 25 '11 at 21:30
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Have there been any studies on the effects of cracking joints outside of the hands? I habitually crack many joints in my body, including but not limited to: fingers, elbows, shoulders, neck, knees, toes, hips, and lower spine. (For what it's worth, I did lots of manual labor and heavy lifting in summer jobs while in high school, but have a desk job now. I also have a few arthritic conditions but my docs think they are genetic.) –  Adam Tuttle Mar 26 '11 at 2:52
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Once again, this is correlation, not causation, and thus, doesn't really tell us anything. I don't think any of you really believe that knuckle cracking causes smoking or alcohol consumption, so I don't see why you'd believe it causes anything else in that list either. –  BlueRaja - Danny Pflughoeft Apr 5 '11 at 19:21
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@BlueRaja: The significant finding here was the lack of a link to arthritis. Correlation tells us little, but a lack of correlation strongly suggests a lack of causation: "In observational studies lack of correlation is easier to interpret than a positive correlation – if there is no correlation between A and B then we can pretty much rule out a causal relationship." –  KonradG Sep 16 '11 at 3:38

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