Man Cracks Knuckles for Decades to Annoy Mother, Science Backs Him

A Nagpur man who has cracked his knuckles several times a day since the age of eleven has presented his mother with scientific evidence that it has done his hands no harm, ending what he calls “a thirty-year cold war”.

“She said I’d get arthritis,” said Mr Sameer Joshi, 41, cracking a thumb for emphasis across the dining table. “She said it every day. At dinner, at weddings, at my own wedding. So I went to the library.”

Mr Joshi’s first exhibit is the work of an American doctor who, told the same thing by his own mother, spent more than sixty years cracking the knuckles of his left hand at least twice a day while deliberately never cracking his right, so that the right could serve as a comparison. In his old age he checked both. Neither had arthritis, and neither was any different from the other. He published the result in a medical journal and later won an Ig Nobel Prize, an award for research that first makes people laugh and then makes them think. “Sixty years,” said Mr Joshi. “One hand. That’s not a scientist. That’s a son.”

His second exhibit is a larger study from 2011, which compared people who cracked their knuckles with people who didn’t, and found that hand arthritis was no more common among the crackers. “That’s two studies,” he said. “She has none.”

His third exhibit, which he plays on his phone at family functions, is an MRI video. In 2015, researchers in Canada put a volunteer’s finger inside a scanner and pulled on it, slowly, until it cracked, filming the inside of the joint as it happened. Mr Joshi now explains what the video shows to anyone who will stand still.

Each knuckle joint, he says, sits inside a capsule filled with synovial fluid, a slippery liquid that keeps the bone surfaces gliding. Like a bottle of soda, that fluid has gases dissolved in it. When you pull or bend the joint, the surfaces separate and the space between them gets bigger, but the capsule is sealed, so no extra fluid can rush in. Instead, the pressure in the fluid falls. Past a certain point, it falls so quickly that the dissolved gas can no longer stay dissolved, and in a fraction of a second a gas-filled cavity forms in the middle of the joint. That sudden event, scientists think, is the crack. They are still arguing about whether the sound comes from the cavity forming or from it partly collapsing a moment later, an argument that Mr Joshi says he is “monitoring closely”.

The gas then takes time to dissolve back into the fluid, which is why the same knuckle can’t be cracked again straight away. “Twenty minutes,” Mr Joshi said. “I have timed it many times.” His wife confirmed that he had.

His mother, Mrs Sunanda Joshi, 68, listened to the full presentation for the fourth time on Sunday. She said she accepted that knuckle cracking did not cause arthritis and that the science was very interesting. She added that she had only ever mentioned arthritis because it seemed more likely to work than the truth. “It was never about your hands,” she said. “It was about the noise. Bring me a study saying that isn’t annoying.”