Cracking your knuckles causes no arthritis: 60 years of proof

Two hundred and fifteen people aged between 50 and 89 came through the surgery of Dr Kevin deWeber, in Pennsylvania, in 2011 so that he could look at their hands. Osteoarthritis showed up in 18.1% of the knuckle-crackers and in 21.5% of those who never cracked them. But the most stubborn piece of evidence is older, and it took sixty years.

Two years earlier, in 2009, an Ig Nobel Prize in Medicine went to Donald Unger, a Californian doctor, for an experiment with a single subject: himself.

Unger had published it in 1998, in a letter to the journal Arthritis & Rheumatism. The design fitted into one paragraph: for more than sixty years he cracked the knuckles of his left hand at least twice a day — some 36,500 cracks — and never once touched the right. Then he compared the two hands. They were indistinguishable.

And all of it because of something said at home. His mother and two aunts had assured him as a boy that if he kept it up he would end up with deformed hands. Unger closed the letter asking, in writing, for someone to go back and check the rest of his mother's advice.