Here’s Exactly What Happens Inside Your Body When You Crack Your Back

There’s something about what happens when you crack your back that’s so unbelievably satisfying. Whether it accidentally snaps and crackles when you stand up or you whip out your best contortionist moves to make it happen, that little pop just feels damn good. If this describes you to a T, you’ve probably been cracking your back for years with no idea as to what, exactly, happens inside your body when you do it.

Clearly nothing is actually breaking, or cracking your back would seriously hurt and be nowhere near as popular as it is. “Cracking your back is very common,” Ferhan Asghar, M.D., assistant professor of orthopedic surgery at UC Health, tells SELF. But what actually produces that resulting noise and feeling of relief? Oddly enough, what’s really happening when you crack your back is up for some debate (more on that shortly). What’s not up for debate is how damn good it feels. So, let’s dive in to all things back cracking!

Here’s an important primer on your spine.
Before you understand what happens when you crack your back, you have to know a bit about your back itself. Down the center of your back you’ll find your spine, which you can think of as “the scaffolding for the entire body,” according to Cedars-Sinai Spine Center. Your spine protects your spinal cord, a bundle of nerves that transmit messages between your brain and pretty much every part of your body. With the help of vertebrae, or interlocking bones, it also supports about half the weight in your body. The average person is born with 33 vertebrae, but most adults only have 24 since some of the lower ones fuse together over time.

Your vertebrae are divided into sections: your cervical spine (your neck bones), your thoracic spine (the upper part of your back), your lumbar spine (lower back), your sacrum (which joins with your pelvis), and your coccyx (tailbone). Your vertebrae connect with each other at the back via flexible joints, and rubbery cushions known as discs are in between each one to provide some cushioning. Finally, your vertebrae connect with muscles, ligaments, and tendons throughout your back to help you do everything from pound out Russian twists at the gym to lean over and whisper in someone’s ear.

Doctors aren’t totally sure why backs crack in the first place.
“There are a number of theories on why this happens, but nobody really knows,” Neel Anand, M.D., professor of orthopedic surgery and director of spine trauma at Cedars-Sinai Spine Center in Los Angeles, tells SELF.

The most widely believed theory comes down to pockets of gas that hang out in your joints. This isn’t the same kind of gas that escapes from your body after you’ve had a ton of beans or protein bars This gas comes from a lubricant inside your joints known as synovial fluid, which helps give nutrients to the cartilage in your joints to help them glide smoothly. Cartilage’s main job in the body is to make sure that whenever you are moving your limbs this way and that, the movement is, and feels, smooth. That’s why it’s a key player when it comes to cracking your back.

When you apply force to your joints, pressure can build up and turn into dissolved gases like oxygen, nitrogen, and carbon dioxide. The thinking is that these gases shift—and emit a cracking noise as they dissipate—when you do an extreme stretch, Dr. Anand says. The gas actually shows up on X-rays and MRIs, and your surrounding tissues quickly reabsorb it after you crack your back, Lisa A. DeStefano, D.O., chairwoman of the Department of Osteopathic Manipulative Medicine at Michigan State University, tells SELF. However, a buzzy 2015 study in PLOS One examined MRIs of knuckles cracking and argued that the cracking actually happens when a gas-filled cavity forms as the joints stretch, not when the gas bubbles themselves collapse.

Either way, having loose ligaments and tendons may play a role, too, since people who have tight ligaments and tendons typically aren’t able to shift in ways that allow them to actually “crack” their back, Dr. Anand says.

There are also some less widely believed theories that have nothing to do with these gases, like that the cracking sound is actually your ligaments and tendons shifting after you apply force to your body, or that it happens because you don’t have much cartilage in the area that you “cracked,” so your joints can’t glide as smoothly as they should. Whatever the mechanism behind cracking your back is, Dr. Anand says it likely applies to other areas you can crack, like your neck and knuckles.

For now it’s a bit of an unsolved mystery just what is happening in your body when you crack your back. But what is very well established is that it feels ridiculously good and satisfying to do it. So, the next obvious question is: Do you need to be worried about cracking your back?

Is cracking your back safe?
The good news is that cracking your back is usually pretty innocuous. “Ultimately, it doesn’t matter why this happens [as long as] it doesn’t hurt,” he adds.

Some of this can change and evolve as you age. For example, as you get older and the cartilage that helps your joints glide smoothly wears out, cracking your back can start to hurt, Dr. Asghar says. That’s a sign you should try to kick the habit before the situation becomes worse.

If you are feeling pain in your back or neck and it’s not getting better (or it’s getting worse), that’s definitely a sign to take a break from cracking your back and to talk to a doctor.

So why does it feel so good to crack your back?
The reason cracking your back feels so good is also up for debate. You tend to build up stress and tightness in the muscles that surround your spine, especially when you’ve been doing something like sitting in front of a computer all day. It turns out there are things you can do if you do sit all day to counteract the effect sitting has on your back and your posture—certain exercises, an ergonomic desk setup, etc. But even when you do all that stuff, it still feels awesome to stretch the muscles, which is pretty much what you’re doing as you crack your back, Dr. Asghar says. “Some people settle for a simple stretch, but others become accustomed to feeling the crack that comes with the extreme end of their range of motion,” he says.

Your spinal cord is also surrounded by sensory ganglia, or groups of cells that send your brain information about things like pain and joint position, according to the National Institute of Neurological Disorders and Stroke. When you crack your back, your brain might interpret your back as being “better” and less tense than before, Dr. DeStefano says, so you might feel some sense of relief. After all, Dr. Anand says, people generally keep cracking their backs because it makes them feel better, whether it mostly comes down to a psychological effect or not. And by the way, while very little feels as good as a nice crack, there are ways to baby your back between cracks, with, for example, core exercises for lower back pain. Also, never underestimate the power of some gentle stretching to loosen things up.

While cracking your own back is largely harmless, be careful about having someone else do it for you.
It’s pretty hard for you to hurt yourself when you’re cracking your back on your own, since you’ll instinctively want to protect yourself from harm, Dr. Asghar says. But when someone else does it for you, they can use more force than necessary or move your body in a different or more extreme direction than they should, Dr. Anand says. “You can hurt your back if they don’t know what they’re doing,” he adds.

Seeing a licensed chiropractor, physical therapist, or osteopath is a different story, though. Under the care of a qualified practitioner, back manipulation can be safe, Dr. Asghar says, and it can be one of many tools experts use to address conditions like chronic back pain. Keep in mind that it’s really important to find someone who’s licensed to do this kind of thing—rapid, aggressive manipulation really isn’t advisable, since it can lead to injury. It’s even caused strokes, in extremely rare cases.

You’ll need to seek out which licensing qualifications are in place for the specific type of expert you want to see, but anyone you go to should give you a thorough physical examination and discuss potential treatment options for whatever ails you before proceeding to any kind of manipulation. A doctor or chiropractor can help you navigate this situation and decide on the best course of treatment and whether it involves having your back manipulated.

If you are having a medical expert manipulate your back and you don’t hear a crack, it doesn’t mean your treatment wasn’t effective. “Often the stretch—short of a crack—along with soft-tissue and muscle mobilization is what does the trick in relieving discomfort,” Dr. Asghar says.

Ultimately, if you feel good when you crack your back, you’re fine to keep doing it. But take a pass on having a friend walk on your back, twist your neck, or do anything else to achieve that crack—it’s just not safe.