Despite probably having been told thousands of times otherwise, cracking your knuckles does not cause arthritis, according to a recent Scientific American article.
The story cites several studies to back up its findings, including a study published in 1998 where for 50 years researcher Donald Unger cracked the knuckles on his left hand at least twice a day while leaving the other hand at rest to serve as a control.
According to the story, that means Unger cracked his knuckles on his left hand at least 36,500 times, “while those on the right cracked rarely and spontaneously.”
So why do conduct this seemingly off-the-wall experiment?
Because, as Unger explains, during his childhood “various renowned authorities (his mother, several aunts and, later, his mother-in-law) informed him that cracking his knuckles would lead to arthritis of the fingers.”
In other words, Unger didn't want his relatives giving him advice without being able to back it up with evidence. And, during the five decades of his test, Unger had the satisfaction of telling those relatives simply that the results weren’t in yet.
Upon completing his study, Unger found the following: “There was no arthritis in either hand, and no apparent differences between the two hands,” which caused him to conclude that “there is no apparent relationship between knuckle cracking and the subsequent development of arthritis of the fingers.”
But though the study almost certainly gave Unger personal satisfaction when presenting his findings to his relatives, he could have saved some time by simply referring to other scholarly studies of knuckle cracking that have already been done, as the article points out.
For example, Dr. Robert Swezey’s own 1975 study — co-authored by his then 12-year-old son in an apparent attempt to get the kid’s grandma to stop the worrying about the cracking — also found that cracking one’s knuckles did not cause arthritis.
Bone development expert David Kingsley at Stanford University had also looked into the theory. He found that Swezey and one other researcher had both determined that knuckle cracking did not lead to arthritis by visiting nursing homes to ask the elderly both whether they had cracked their knuckles and whether they had arthritis.
Neither found an increased arthritis incidence among the crackers, so it’s officially safe to crack away.