During the opening scene of “Birdman,” the Oscar-winning movie about a washed-up action star trying to revive his celebrity status, Michael Keaton meditates in his Broadway dressing room, eerily levitating off the floor, before cracking his neck twice. That one move makes it clear: this guy is tense.

Some people crack their necks like others crack their knuckles — out of habit. The result is the same: You burst a small gas bubble inside the joint, causing that popping sound, according to experts at Johns Hopkins Arthritis Center. Here’s the science behind the pop: Every joint is encased in a capsule that contains synovial fluid, a nutrient-rich lubricant. When you crack your neck or bend your finger a certain way, you stretch the capsule and lower the pressure inside it, creating a vacuum. That vacuum is quickly filled by gases (nitrogen, carbon dioxide), which are released when you burst the bubble.

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“People worry a lot about the sounds their joints make and the sounds their body makes, and in general we don’t think it’s much to worry about,” says Steven Vlad, MD, a rheumatologist at Tufts Medical Center in Boston.

“There’s a famous story among the rheumatology community about this rheumatologist who cracked the knuckles of one hand every day for his whole career and didn’t crack the fingers of his other hand,” says Vlad. “And there was no difference in his hands by the end of his life.”

Whether it’s safe to have your neck “cracked” (more accurately, manipulated or adjusted) by a chiropractor is more a matter of debate.

In a 2012 article in the British medical journal BMJ, a group of researchers from the United Kingdom and Australia advised against the practice because it could potentially damage major neck arteries and lead to stroke. A separate group of researchers, led by epidemiologist David Cassidy, PhD, of the University of Toronto, argued in the same journal that that evidence doesn't support a direct correlation between strokes and manipulation, and that cervical spine (neck) manipulation is a valuable addition to patient care that has a significant effect on short-term pain. 

Since then, in 2014 in the journal Stroke, the American Heart Association and the American Stroke Association issued a statement about the connection between cervical spine manipulation and stroke, saying that “although the incidence is … probably low, and causality difficult to prove, practitioners should consider the possibility” of stroke and inform patients of the risk before performing the procedure. 

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Austin Davis, DC, a San Francisco-based chiropractor, says skill comes into play. “Chiropractic, practiced properly, has no threat of stroke,” Davis says. “But like a mechanic who doesn’t know what they’re doing — they can burst the brake line — anybody in any profession who doesn’t know what they’re doing has the potential of hurting somebody.”

Davis recommends vetting your chiropractor before making an appointment.

  • Choose a doctor you feel comfortable with — someone who will listen to you and explain what they’re doing.
  • Make sure he has attended an accredited chiropractic school.
  • Ask about their philosophy, how they practice and what they plan on doing to keep you healthy.
  • Be wary of chiropractors who seek to treat only the symptoms and not the cause. “Chiropractic is about cause. We want to find out the cause and if there’s an interference to your nervous system.”

And as for cracking your neck (or back) yourself, Davis recommends leaving it to the pros. He says he sees patients do more harm than good when they try to readjust their spine themselves because they don’t know the specifics of how their body is out of alignment.

Spinal adjustment serves a specific purpose, says Davis: realigning the spine so the brain and body can communicate properly with the nervous system, all the way down the brainstem, cervical spine and the spinal cord.

“If it’s shifted to the right and they’re pushing right, they could actually push it further out of place,” Davis says. “They’ll still hear a noise, they’ll feel better because their brain is tricking them into feeling better, but ultimately they’ll do more harm than good.”

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Nicole Cammorata is a Brooklyn-based writer, editor and content strategist.