I don’t remember how old I was when I first heard someone say, “Don’t crack your knuckles! It’ll give you arthritis!” But I do know that ever since then, I’ve felt a weird pang of guilt any time I do it.
Although not everyone enjoys hearing it, there’s something so satisfying about that familiar cracking sound accompanied by the feeling of release in your fingers. As with eating lots of candy and other nice things in life, the notion that this habit isn’t particularly good for your health doesn’t feel inconceivable.
Still, is the whole “cracking your knuckles causes arthritis” thing even based in scientific fact? We asked doctors to weigh in.
What’s happening when you crack your knuckles?
“The sound produced by cracking knuckles [comes from] nitrogen bubbles in the synovial fluid that is found within the joints in the body,” said Dr. Jason Liebowitz, a rheumatology specialist in Rockaway, New Jersey. “Synovial fluid is a natural substance that helps lubricate the joints.”
Basically, synovial fluid allows for healthy movement and helps protect the cartilage from wear and tear. When you crack your knuckles, you create negative pressure, which leads to the generation of bubbles in the fluid.
While experts previously believed the cracking noise was the “pop” or collapse of bubbles, more recent research suggests the sound may actually stem from their formation.
“This phenomenon occurs primarily in small joints of the hands and facet joints in the spine ― responsible in part for ‘cracking your back,’” explained Dr. Robert G. Hylland, an assistant clinical professor at the Michigan State University College of Osteopathic Medicine. “Those people with looser joints can’t generate enough negative pressure to create bubbles, explaining why some people can’t crack their joints.”
You may have noticed that after you crack your knuckles, you can’t just immediately do it again and again. There’s a biological reason for that as well.
“It takes about 20 minutes for these cavities, or bubbles of vapor, to refill,” said Dr. Iziegbe Ehiorobo, a rheumatologist at the Ohio State University Wexner Medical Center. “Hence it might take that long before a knuckle can be cracked again.”
Does it cause arthritis?
“There is no evidence that ‘cracking knuckles’ is associated with the development of arthritis, thus it is not in any obvious way bad for one’s health,” Liebowitz noted.
Many studies over the years have failed to find any correlation between knuckle-cracking and arthritis ― an umbrella term for a number of conditions involving joint inflammation or damage. Ehiorobo pointed to a famous decadeslong experiment from Dr. Donald Unger as further proof that there’s no relationship between knuckle-cracking and arthritis.
“Donald Unger performed an experiment on himself to test the hypothesis that knuckle cracking increases the risk of arthritis,” he explained. “For over 50 years, he cracked the knuckles of his left hand at least twice a day and left those of the right hand for control. He then compared both hands at the end of the experiment and found that there was no arthritis in either hand. Also, there was no difference between the hands.”
Although the medical community feels confident that the habit doesn’t increase your risk for arthritis, there’s less certainty around the origin of this widespread myth.
“How this common misconception got started is not clear, but I suspect the commonality of osteoarthritis in the hands as we age and the commonality of knuckle-cracking, along with the distinct noise thus created, were all factors,” Hylland said. “Given the annoying nature of the sound, I suspect parents were quick to use these observations to halt the behavior and, eventually, repetition through time solidified its justification.”
What about other health issues?
OK, so cracking your knuckles doesn’t cause arthritis. But is it bad for you in other ways?
“There is no evidence that the process of cracking knuckles can cause arthritis, but it can rarely damage the tendons that connect muscle to bones,” said Dr. Scott Zashin, a Dallas-based internist and rheumatologist.
Indeed, Harvard Health Publishing notes that there have been “occasional reports” of injuries related to “overly vigorous knuckle-cracking,” but emphasizes that these are extreme exceptions. A 1990 study also found knuckle-cracking might be linked to swollen hands and lower grip strength.
Still, these potential adverse affects seem to be extremely rare. The real concern may simply related to psychological aspects of the habit.
“There is no apparent damage caused by this activity save the annoyance it tends to provoke in people nearby,” Hylland said. “Many people feel a sense of relief, albeit short lived, after cracking their joints, suggesting that joint tightness may create some sense of discomfort for them. This cycle of tightening, cracking, tightening, etc. may promote the habit that some find difficult to break.”
And no medical experts are touting any health benefits to incessant knuckle-cracking.
“While it may be comforting for some people and used by others to deal with stressful situations, there is no evidence to suggest that it is good for the joints,” Ehiorobo said.
So what does cause arthritis?
Getting back to the myth that knuckle-cracking causes arthritis, a question still remains: What does cause arthritis?
“In terms of types of arthritis that do exist, the most common is osteoarthritis,” Liebowitz said. “Although it is more complex than a simple one-liner, osteoarthritis is, generally speaking, the narrowing of the joint space that results from loss of cartilage (such as articular cartilage lining the joint) and causes aches and pains, particularly with use or changes in weather.”
He added that there are many forms of arthritis, and they can be caused by autoimmune diseases (as with rheumatoid arthritis and psoriatic arthritis), crystals depositing in a joint (as with uric acid crystals from gout), infections (like staphylococcal or Lyme disease), medications and other issues.
Some arthritis is hereditary and related to mutations in genes for collagen. However, genes alone aren’t the cause. There are many unknowns.
“A lot of things can cause arthritis ― genetics, your environment, your activity, so many things can impact the way our joints work,” said Dr. Nilanjana Bose, a rheumatologist at Lonestar Rheumatology in Houston. “There are a lot of variables that go into who develops symptomatic arthritis and who doesn’t.”
If you experience unusual joint pain, stiffness or swelling, seek medical attention and find out if arthritis might be the culprit.
“Anyone who has arthritic pain deserves an evaluation,” Bose said. “These days rheumatologists are available. That makes care a lot of more accessible. There are tools to help.”