If 2010 was the year you were going to stop cracking your knuckles, you may want to consider another resolution.
Despite what such renowned authorities as your mother might say, the obnoxious habit does not lead to arthritis of the fingers, according to several studies, including one by California doctor Donald Unger, who was recently recognized for his hands-on research about the topic.
For 50 years, Unger popped the knuckles of his left hand at least twice a day, leaving his right hand as a control. "Thus, the knuckles on the left were cracked at least 36,500 times, while those on the right cracked rarely and spontaneously," he wrote in a letter to the editor in the journal Arthritis & Rheumatism in 1998.
Unger's data set showed no arthritis in either hand and no apparent differences between the two hands, a finding that earned him the 2009 Ig Nobel Prize in Medicine, a Nobel Prize parody that is awarded to research projects that "first make you laugh, then make you think." (With the Igs, it's irrelevant when the research was done.)
"With Dr. Unger all we can say is that his time had come," said Marc Abrahams, organizer of the awards.
Unger conceded that a larger group would be necessary to confirm his findings but said the results call into question whether other parental beliefs, such as the importance of eating spinach, are also flawed. "Further investigation is likely warranted," he wrote in his 1998 report.
Dr. Robert Swezey, whose 1975 study also found that children's knuckle-cracking was not linked to arthritis, criticized Unger's research method because it was not a blind study. Unger knew which knuckle was being cracked, which may have affected his results.
"Blinding would only be possible if the investigator didn't know left from right," he wrote in a tongue-in-cheek commentary in the journal. "This is not likely since studies indicate that only 31 percent of primary care physicians don't know left from right. (The figure is reportedly somewhat higher for most specialists.)"
A slightly larger — and more rigorous — 1990 study by Detroit researchers found that habitual knuckle-crackers were not at higher risk for arthritis. But they were more likely to experience hand-swelling and lower grip strength.
Reached in his office in Thousand Oaks, Calif., Unger, 83, is still a little puzzled by all the attention, which comes 11 years after his letter was published. As a past president of the American College of Allergy, Asthma and Immunology and the author of more than 40 research papers, he says "to become 'famous' for this stupidity seems very strange."
Yet Unger remains good-natured about his 15 minutes of fame. He has already decided what his follow-up act will be. "Most tombstones are an absolute bore," he said. "Mine will say, 'Here lies Don Unger, who finally quit cracking his knuckles."'