It happens to us all: You stand up after sitting for a while and you hear a loud "pop." Why do knees do that? Is it bad?

Here are the short answers: 1) crepitus and 2) probably not, but possibly yes. Read on to find out why this happens, and when it's worth worrying about.

See What Is Crepitus?

Popping knees can be alarming, but are usually not a cause for concern. Crepitus in the Knee

Why joints pop

Like nearly all the joints in your body, the knee joint is covered by a protective membrane containing synovial fluid. This fluid lubricates the joint, allowing it to move smoothly and easily.

Learn more: What Is a Synovial Joint?

Occasionally, tiny gas bubbles build up in this fluid. When the joint moves, the bubbles are released, causing the nearby ligaments to emit a snap or pop sound. The technical term for this phenomenon is crepitus, which also describes all grinding or crackling sounds and sensations in the body.

See Crepitus in the Knee


When to be concerned about joints popping

Most of the time, this popping and creaking of joints is harmless. However, crepitus is also a symptom of the joint degeneration that leads to osteoarthritis.

You should worry about joint popping if:

  • It's occurring frequently in one location
  • It's accompanied by pain
  • It's accompanied by joint swelling, tenderness, or stiffness
  • You're also having pain as a result of prolonged joint movement, such as when walking

If you're experiencing pain when a joint pops or you have any other of the symptoms listed above, talk with your doctor. If your symptoms and test results indicate it, your doctor may diagnose osteoarthritis and start treatment. Treatments for osteoarthritis can ease pain, improve mobility, and slow disease progression—especially if it's caught early.

See Osteoarthritis Treatment

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Carrie DeVries worked as the content marketing manager at Veritas Health. She combined a background of writing and editing, marketing, and patient education to best serve the consumers, patients, and physicians who rely on Veritas Health for information.