Donald Unger, a medical doctor, cracked the knuckles of his left hand every day for more than sixty years, but 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.
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headless-horsey: i tell my dad about this every time he says something about me cracking my knuckles and he never listens.