Tell Me Why My Joints Pop

Tell Me Why My Joints Pop

Get the scoop on why joints snap, crackle and pop.

Joints—you forget you have them until you bend your knees and sound like a bowl of Rice Krispies –-snap, crackle and pop! So why do joints pop? The answer isn’t so simple.

“Joints pop for a variety of reasons,” says John Bojescul, MD, an orthopedic surgeon with Doctors Hospital of Augusta in Georgia. It usually happens because of the fluid and mechanics of the joint when you bend and stretch, he says.

The noises, called crepitus, may come from a tendon moving across a joint. Or you may have momentarily (and harmlessly) broken the seal of synovial fluid that fills the joint capsule. Additionally, arthritis can make joint surfaces rough and cause friction when they move.

Although it can make you feel old, cracking sounds from your joints usually are nothing to worry about. However, if you’re hearing noises and experiencing pain and swelling, it could be a sign of something more serious that should be checked by your doctor, says Dr. Bojescul. “If your primary care doctor is not comfortable with [treating] your injury, he or she will send you to an orthopedist or physical therapist,” he says.

Knuckle Cracking
Can’t resist cracking your knuckles? Don’t worry. You’re not doing lasting damage. The sound you hear is a gas bubble forming. When you crack your knuckle, the space in the joint expands and all the gas dissolved in the synovial fluid rushes to fill that space (like how fizz is released from soda when you open the bottle) and it makes a pop sound.

And what about that age-old saying that cracking your knuckles causes arthritis? “I don’t think anyone has a true answer to that, but I haven’t seen it in my experience,” says Bojescul.

In fact, a 2011 study found that people who didn’t crack their knuckles were slightly more likely to have arthritis than those who did, although the results could have been due to random chance.

Cracking your knuckles can, however, cause chubby fingers. “If you’re constantly cracking your knuckles, your body will eventually respond with inflammation, which can lead to what’s perceived as bigger fingers,” says Bojescul.

Bottom line: It’s completely normal for joints to pop, but if you ever experience pain or swelling, talk to your doctor. And as for you knuckle crackers out there—well, you can keep it up so long as you don’t hurt yourself.

See More from Dr. Bojescul:
What is the function of the synovial fluid in joints?
What is a ball and socket joint?
How can I prevent pain and stiffness in my joints as I age?

Medically reviewed in November 2018.

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