There are certain sounds you expect to hear during a workout: heavy breathing, weights clinking on the rack, and the catchy melodies of a pump-up playlist. One that may very understandably catch you off guard? The cracking or popping in your knees as you lower down or stand up from a squat.

We get it, hearing that creak can be alarming. But let us offer some reassurance: “It’s pretty common,” physical therapist Brendan Overlid, DPT, CSCS, of UCHealth in Colorado, tells SELF. Even his knees do it on the reg, he says, and in lots of cases, it’s actually NBD.

The official term for joints making noises is crepitus, and when we’re talking knees specifically, there are a lot of different things that may cause this body part to “make a little bit of ruckus” when you squat, physical therapist Nicole Haas, PT, DPT, founder of Boulder Physiolab in Colorado, tells SELF. Here, we dig into what might be going on there—and whether it’s possible to calm that creaking.

1. Sorry, but you’ve got gas (not that kind).

Sometimes, that cracking or popping sound you hear as you push your hips back really just boils down to gas, since bubbles can naturally form in the fluid that surrounds your knee joint. When you bend your knee in a squat, you close that space and ultimately cause the bubble to pop and emit a sound, physical therapist Ryan Chow, PT, DPT, founder of Reload Physical Therapy and Fitness in New York City, tells SELF.

It’s the same mechanism that often causes popping and cracking noises in other joints, like your knuckles, for example. Typically, this type of sound comes with a release in pressure and is followed by a refractory period—meaning, there’s a certain amount of time you have to wait until that same pop would happen again, Dr. Overlid explains. So if you sink into a squat and hear a single squeak, but then start busting out some blessedly silent reps, this may be what’s going on.

What to do about it: Honestly, nothing. This is just one of those natural bodily functions!

2. Some harmless form quirks might be to blame.

The squat is a compound exercise, which means it involves many different muscles and joints working together, Dr. Chow explains. Given all the synchronization that has to happen, it makes sense that there can be lots of little nuances in how people squat. In some cases, these slight form quirks can lead to popping noises. For example, some people might inadvertently place more weight on the outside of their foot than the inside, and this uneven distribution can cause a buildup of pressure in the knee that ultimately leads to a cracking sensation and sound, Dr. Chow says.

In other cases, foot positioning can play a role—particularly, if you try to force a stance that’s not natural to you. In that case, you restrict your knee joints from moving freely and instead place extra stress on them, which can ultimately lead to a build up in pressure that causes that snap, crackle, or pop noise, Dr. Chow explains.