Studies show that around 20% to 50% of Americans crack their knuckles. While those who crack might find the sound satisfying, those within hearing range might find it anywhere from distracting to maddening. But what causes the pop—and is it merely an annoying habit or is it harmful to the joints?
According to Joseph Medellin, M.D., a sports medicine physician with Henry Ford Allegiance Health, the cracking sound happens when you stretch or bend your finger bones backward, pulling them apart. This increases the space between the joints and causes gas bubbles to burst in the fluid that lubricates the joints. (That’s called synovial fluid.) You can’t crack the same knuckle again right away because it takes time for the gas bubbles to reaccumulate.
While it might feel like cracking knuckles relieves tension and makes the joint more mobile, there is no evidence this is true. It’s more likely that the only benefit is easing emotional stress and occupying your hands when you’re nervous.
Similarly, Dr. Medellin says there is no real harm in the practice. “There is no evidence to support the old wives’ tale that says cracking knuckles causes arthritis of the hands,” he says. That myth probably originated with people who wanted to convince knuckle crackers to quit.
There have been rare cases of ligament sprain from unusually forceful cracking of the knuckle. It’s also possible—but not easy—to pull the finger out of the joint. A 1990 study found that regular knuckle cracking may decrease grip strength.
“Knuckle cracking should not be painful or cause joint swelling,” says Dr. Medellin. “If you notice such signs, it’s best to see your doctor to determine a possible underlying condition. Certainly seek help if you accidently dislocate your finger!”
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Joseph Medellin, M.D., is a sports medicine physician with Henry Ford Allegiance Health. He is dedicated to serving high school and college athletes in south central Michigan. Dr. Medellin also promotes the health of families through a collaboration with the Dahlem Environmental Center and its Nature for All Trail. He is the head team physician for Albion College, Jackson College and Spring Arbor University.