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Knuckle Cracking: Annoying or Harmful

Despite how common knuckle cracking is, there has been considerable debate regarding where the noise comes from, and whether it cause long term effects to your joints. Knuckle cracking is a common behavior that many people perform on a daily basis. It can become a habit as a way to deal with nervous energy, a way to “release tension,” loosen stiff fingers, or it’s simply an annoying thing that other people do.

Before we delve into what causes the noise, here are some fast facts on knuckle cracking:

  • Between 25 and 54 percent of people crack their knuckles.

  • Most knuckle crackers are male.

  • The cracking sound has been linked to the formation of bubbles in the synovium; with synovial fluid rushing into the joint.

  • Cracking knuckles does not appear to cause or worsen arthritis, but it can soften the grip and lead to soft tissue swelling.

The “cracking” seems to be produced by increasing the space between finger joints. This causes gas bubbles in the joint fluid to collapse or burst. It’s a bit like blowing up a balloon and then stretching the walls of the balloon outward until it pops. The reason you can’t crack the same knuckle or joint twice right away is that it takes some time for the gas bubbles to accumulate again in the joint.

One of the most convincing bits of evidence suggesting that knuckle cracking is harmless comes from a California physician who conducted an experiment on himself. Over his lifetime, he regularly cracked the knuckles of only one hand. He checked x-rays on himself after decades of this behavior and found no difference in arthritis between his hands. A larger scientific study resulted in the same conclusion.

There are rare medical reports of problems associated with this behavior that may relate to how much force is applied and one’s particular technique. For example, joint dislocations and tendon injuries have been described after attempts to crack knuckles. One study published in 1990 found that among 74 people who regularly cracked their knuckles, their average grip strength was lower and there were more instances of hand swelling than among 226 people who did not crack their knuckles. However, the incidence of arthritis was the same in both groups.

If cracking knuckles is caused by synovial fluid rushing into the joint, can that have an impact on your risk for arthritis? Contrary to many people’s fears, the science suggests that no — it is not. Several large clinical studies have examined patients with osteoarthritis — a.k.a. “wear and tear” arthritis, the most common form — to determine how many of them are “knuckle crackers.”

Scientists have found no evidence to suggest that people who crack their knuckles have higher rates of arthritis or other bone conditions than those who do not crack their knuckles. In fact, one man used himself as a test case, cracking only the joints on his left hand but not his right. Believe it or not, after more than 60 years of doing this, there was no difference in arthritis between the two hands.

Of course, cracking a joint does cause the material holding the joint and surrounding connective tissue to stretch. Over time, repeated joint cracking can loosen the tissue. This makes it easier to crack the joints — and that’s why knuckle crackers have joints that are particularly susceptible to popping. However, this appears to be a harmless side effect of knuckle cracking. Loosened connected tissue as a result of frequent knuckle cracking has not been associated with disease.

The conclusion? If you want to crack your knuckles, it’s unlikely to cause you harm. If you stretch or pull a finger to the point you experience an injury, such as a dislocated joint and and injury to a tendon, seek medical help immediately.

But if you want someone else to stop cracking their knuckles, you’ll need a better reason than telling them they’re ruining their joints.

For more information or to request an appointment, please contact Dr. Patrick McDaid, M.D. at

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