Whether your knee, shoulder, or some other body part has been popping since you can remember or the noise is more of a recent development, you’ve probably wondered what it means. Dear reader, it’s time to talk about crepitus. Crepitus is a pretty creepy-sounding medical term that describes all the audible snaps, crackles, and pops your joints might make when you change positions or move a certain way. (Seriously, it’s even the title of a horror movie.)

There’s a lot doctors don’t understand about crepitus, but there are some theories as to why and how it happens. Let’s get to it.

For the record, it’s completely normal to experience crepitus here and there as long as it doesn’t cause pain.

Crepitus generally happens when joints or ligaments rub together as you move or compress them, according to Kelley and Firestein’s Textbook of Rheumatology. Since this medical term encompasses cracking noises everywhere from your knuckles to your back and more, it’s clearly pretty common, John-Paul H. Rue, M.D., sports medicine and orthopedics specialist at Mercy Medical Center, tells SELF. Crepitus can be fine, which is more of a mild creaking sound and sensation, or coarse, which is more intense.

There’s quite an interesting debate about what causes the creaking noises coming from your body.

Crepitus isn’t yet well-understood in the medical world, Dr. Rue says, but experts have done some digging on why exactly it happens. It could simply be that moving your body in a certain way makes some of your inside bits grind together, emitting a noise in the process. “[Crepitus] can just mean that the tissue is snapping when it rubs over something, like a ligament snapping over the edge of a joint,” Timothy Gibson, M.D., orthopedic surgeon and medical director of the MemorialCare Joint Replacement Center at Orange Coast Medical Center in Fountain Valley, California, tells SELF.

What about when you force certain parts of your body to crack, like your knuckles? The most well-established theory there is that the noise is all about...well...gas. Surprise!

OK, so there’s this liquid inside your joints called synovial fluid that helps your joint cartilage glide more easily. (Your joint cartilage is a slick substance that shields the edges of your bones, basically, so that you can move freely and without discomfort.) If you push, pull, or otherwise manipulate your body in a way that puts force on your joints, that pressure can become bubbles of gas, like carbon dioxide or nitrogen, that might pop and let out a sound.

An opposing notion holds that the sudden creation of a new space within the joint (like from pulling it) makes the sound, not the collapse of gassy little bubbles.

“Either way, cracking, popping, or snapping itself does not appear to be either harmful to the joint or a marker of any specific disease or condition,” Dr. Rue says.

The only time crepitus is really a problem is if it comes along with pain or compromised mobility.

If your joints pop sometimes when you move a certain way but they don’t hurt or otherwise bother you, it’s probably nothing. “Painless ... noises like popping joints or cracking knuckles do not by themselves require any specific evaluation or treatment,” Dr. Rue says.

Experiencing pain with your crepitus is another story, Dr. Gibson says. Ditto if you have swelling associated with the creaking, squeaking, or grinding of your joints, or if you have a feeling that the joint is getting “stuck” or locked in a certain position, Dr. Rue says. In those cases, you should see a doctor.

In certain cases, crepitus can be a sign of osteoarthritis, which is a common form of arthritis that happens when that protective joint cartilage wears down over time, the Mayo Clinic says. “With osteoarthritis, as joints wear out, the normal smooth cartilage may become thinner or irregular,” Dr. Rue says. “As these worn-out joint surfaces roll or glide across each other, the joint may make noise.” Osteoarthritis can also cause joint pain, tenderness, and stiffness, and bone spurs, which are spiny protrusions that can lead to more pain and difficulty moving.

Rheumatoid arthritis, which is a chronic inflammatory disorder, can also lead to crepitus, Dr. Gibson says. This condition happens when your immune system accidentally damages the lining of your joints, and it can eventually lead to bone and joint erosion resulting in crepitus. Other symptoms of rheumatoid arthritis include sore, warm, and swollen joints, joint stiffness that’s usually worse in the morning and after inactivity, and fatigue, fever, and weight loss, the Mayo Clinic says. It can also affect other systems of your body, causing issues such as dry eyes and mouth, infections due to compromised immune function, and shortness of breath.

It’s also possible to deal with crepitus after sustaining an injury that damaged your cartilage, like tearing your meniscus, one of the C-shaped bits of cartilage in your knee, Dr. Gibson says. Anything that makes structures in your body swell so that they might rub against other ones can cause crepitus, too, Dr. Rue says. Think: tendinitis (inflammation of your tendons, which attach your muscles to your bones) or bursitis (inflammation of tiny fluid-filled sacs that shield the bones, tendons, and muscles near your joints).

There’s no treatment for crepitus itself, but if yours is painful, hampers your movement, or just feels off in some way, you should definitely call your doctor.

Based on your specific symptoms, they can perform some exams and run tests to determine the cause of your crepitus.

If your crepitus is due to age-related wear and tear from osteoarthritis, over-the-counter pain-relievers like nonsteroidal anti-inflammatory drugs might help other symptoms of this condition, like joint pain. Your doctor may want to put you on a prescription version if your symptoms are severe, according to the Mayo Clinic says. Physical therapy could be a good idea, too, since it may help you improve your joint and muscle strength, making it easier to move and cutting back on discomfort. There are also surgical treatments for osteoarthritis if necessary, like injecting your joint with cortisone to help with pain.

What if your crepitus is happening because of some kind of inflammation, like tendinitis? Your doctor might recommend anti-inflammatory medications and the R.I.C.E method: rest, icing the area for 20-minute periods multiple times a day, compressing the area, and elevating it as well. In more severe cases, your doctor may suggest corticosteroid injections to help reduce inflammation, along with physical therapy to strengthen that part of your body, the Mayo Clinic says—but it really depends on what exactly you’re dealing with.

And if it turns out your crepitus is tied with a condition like rheumatoid arthritis, your doctor will work on treating that underlying cause with some of the above methods. NSAIDs, corticosteroids, and applying warmth or cold may offer relief, as can drugs meant to impede how quickly your RA is progressing, the Mayo Clinic says. Physical therapy to keep your joints as supple as possible is one of the many other options for treating rheumatoid arthritis, though the condition may require surgery to address joint damage that’s really giving you trouble.

So, what’s the real takeaway here? The human body has an abundance of weird, cool quirks, and sometimes that cracking sound when you move is just one of them.