What cracking your knuckles actually does to your bones and joints

Snap, crackle and pop. Those sounds can either make you cringe, or induce a sense of relief — it really all depends on how you feel about knuckle cracking.

Some believe that cracking your knuckles can lead to the development of arthritis or other joint issues, but how much truth is there to those claims? Can that cracking lead to actual harmful repercussions, or is it just an annoying habit?

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According to Dr. Robert Shmerling of the Beth Israel Deaconess Medical Centre, people crack their knuckles for a few reasons.

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Evidence suggests that what happens in the joints, he says, is that gas bubbles accumulate in the joint (which is normal) and when that space in the joint is expanded by the manipulation of the joint when cracking it, the gas bubbles burst — that is what causes you to hear that sound. It also explains why you cannot crack the same joint again for a while, because the gas bubbles need to accumulate again.

For a while, many thought that arthritis developed as a result of cracking one’s knuckles, but that was just a medical myth, Shmerling clarifies.

But engaging in the habit is usually not harmful, he says.

Shmerling mentions an experiment one California physician conducted on himself. Over this man’s lifetime, he would crack the knuckles on one hand, but not on the other. When he x-rayed himself after years of doing this, he found no difference in arthritis in either hand. A larger study in the 1970s later came to that same conclusion.

But even though there hasn’t been any evidence finding arthritis developing as a result of cracking knuckles, Harvard Medical School does say there is a chance of having swollen hands and a reduction in grip strength over time.

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However, there is still a chance for injury, Shmerling warns.

“There are rare reports of dislocation or tendon injuries from knuckle cracking,” he says. “They probably represent ‘over-enthusiastic’ joint manipulation or, perhaps, knuckle cracking in a person whose joints were unusually flexible.”

One small 2011 study, however, found that cracking your knuckles may leave you open to developing metacarpophalangeal join osteoarthritis. More than 200 patients between the ages of 50 to 89 years old were looked at and it was concluded that there was a 20 per cent chance of them developing the ailment in their hands after cracking their finger joints over a five-year period.

As to whether or not this theory applies to other joints within the body, Shmerling doesn’t seem to think it’s actually an issue because we cannot readily crack other joints the way we do with finger joints.

“Other joints, such as the wrist, elbow or kneed, are more difficult — or perhaps impossible — to manipulate in a way that would increase the volume of the joint space,” he points out. “There are other sounds that can come from joints — they probably come from tendons rubbing over a bony prominence or, in the case of the kneecap, a bone moving over another bone.”

In general, he says, if there is no pain, “locking” or feeling instability, most sounds coming from the joints are not a cause for concern and do not mean the joint is arthritis or abnormal.