A doctor cracked one hand's knuckles for fifty years

One physician decided to settle the question with his own hands. For 50 years, he cracked the knuckles of his left hand at least twice a day, leaving his right hand as a control that cracked only rarely, on its own.

He published the results himself in a short letter to a medical journal: after five decades, neither hand showed any sign of arthritis, and there was no detectable difference between the cracked hand and the control hand on exam. The sample size was exactly one person, and he said so plainly in the paper.

The letter was written partly as a joke at the expense of relatives who had warned him for decades, and it later won an Ig Nobel Prize for research that makes people laugh and then think. Larger studies with more participants have since reached a similar conclusion, finding no link between habitual knuckle cracking and arthritis.

Fifty years, zero arthritis, one punchline.