The human body is full of surprises — and sometimes, it just refuses to stay quiet about it.

Here’s looking at you, knees. Why do our knees crack when we stand, sit or squat? And is there anything we can do about it?

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Usually, a single “pop” or “crack” is just air moving around in your knee.

This tends to happen when you’ve been in one position for awhile. When you finally bend or straighten your knee, it might sound like snap or pop, or like a knuckle cracking.

As long as it doesn’t hurt, it’s harmless — just air bubbles doing their thing.

“A single, painless pop or crack is usually due to pressure changes in the joint,” says J. Kristopher Ware, MD, an orthopedic surgeon with the Hartford HealthCare Bone & Joint Institute. “Gas bubbles are coming together, then spreading out again.”

Will it cause arthritis, though? Turns out, that’s a myth.

“We do not have any convincing evidence that painless, intermittent cracking of any joint will lead to arthritis,” says Dr. Ware.

> Related: Am I Too Old to Get My Knee or Hip Replaced? What to Consider at Age 70, 80 and Up

If it’s more like a crackle, crunch or grinding, it may have to do with your knee cartilage.

“Some patients describe this sound as ‘rice crispies,’” says Dr. Ware. “It most commonly occurs due to cartilage changes behind the knee cap.”

That could be from a sudden injury, or simple wear and tear. Athletes are especially prone to a condition called chondromalacia patella, where the cartilage softens and breaks down over time.

Any of the above can rough up your cartilage, which means your bone won’t slide as easily in the joint — and you’ll hear about it.

For many people, it’s nothing to worry about. In some cases, though, it can be an early sign of osteoarthritis. So keep your doctor posted.

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If it hurts, swells or makes you wobbly, schedule an appointment.

When paired with symptoms like pain or swelling, all those sound effects can mean something serious is going on with your knee — like arthritis, a tear in the tissue or ligament, an issue with your knee cap, or something else.

“Cracking that’s associated with pain, swelling, or a sense of instability of the joint should be evaluated by a medical professional,” says Dr. Ware.

That’s important for your short-term relief. It’s also important long-term, because many conditions can lead to arthritis if they’re not treated properly.

To stop your knees from cracking (some), focus on healthy habits.

You’ll probably always hear the occasional snap, crackle or pop from your knees. But some wellness habits can make it happen less — in particular, maintaining a healthy weight and exercising regularly.

“Although there’s no way to prevent all joint noise, you can maintain your knee health through regular physical activity, especially aerobic and resistance exercises for the lower extremities,” says Dr. Ware. Think: biking, swimming and leg day at the gym.

You’ll be healthier than ever. Your knees may just have less to say about it.