The common claim that cracking one’s knuckles causes arthritis appears unsupported. A recent study examined the hand radiographs of 215 people (aged 50 to 89) and compared the joints of those who regularly cracked their knuckles to those who did not. The study concluded that knuckle-cracking did not cause hand osteoarthritis, no matter how many years or how often a person cracked their knuckles. An earlier study also concluded that there was no increased preponderance of arthritis of the hand of chronic knuckle-crackers; however, habitual knuckle-crackers were more likely to have hand swelling and lowered grip strength. Habitual knuckle-cracking was associated with manual labour, biting of the nails, smoking, and drinking alcohol and was suggested to result in functional hand impairment. This early study has been criticized for not taking into consideration the possibility of confounding factors, such as whether the ability to crack one’s knuckles is associated with impaired hand functioning rather than being a cause of it.
Medical doctor Donald Unger cracked the knuckles of his left hand every day for more than sixty years, but he did not crack the knuckles of his right hand. No arthritis or other ailments formed in either hand, earning him the 2009 Ig Nobel Prize in Medicine, a parody of the Nobel Prize.