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Grinding knees, should I be worried?

Nov 2, 2023

Why Does My Knee Make That Noise? Understanding Knee Crepitus

Ever hear a strange sound coming from your knee — maybe a grinding, popping, or even a snap, crackle, or pop? You’re not alone.

In fact, 99% of knees make some sort of noise, according to research by McCoy et al. This common phenomenon is called knee crepitus, and while it can sound dramatic, it’s usually not a cause for concern.

🦵 So, what exactly is knee crepitus?

Crepitus is a term used to describe grinding, popping, or cracking sounds from a joint, often accompanied by a subtle vibration or sensation. It can be alarming — but most of the time, it’s completely harmless.

Let’s break it down into two main types:

⚠️ Pathological Crepitus

This type of knee noise is linked to a specific injury or structural issue. It might come from:

  • ACL or meniscal tears

  • Degenerative changes (like osteoarthritis)

  • Patellofemoral instability

  • Post-surgical changes

People with pathological crepitus often report pain, swelling, or joint effusion (fluid on the knee). In these cases, seeing a physiotherapist is the right move — early rehab can make a big difference.

✅ Physiological Crepitus

This is the much more common kind — and it’s not harmful.

It’s simply a noise. There’s no injury, no pain, no swelling. In fact, many people can’t even explain when or how the noise began. You might hear it during squats, stairs, or just moving around — but it doesn’t mean your joint is damaged.

🔍 What causes these sounds?

The exact cause can vary:

  • Cavitation (not bubble collapse): New MRI studies suggest the sound may come from tiny gas cavities forming in the joint.

  • Tendons snapping over bony landmarks — for example, the biceps femoris tendon on the outside of the knee.

  • Ligament movement or soft tissue shifts during motion.

If you’re curious about the science, we recommend this engaging TED-Ed video on why joints pop.

🧠 Could it be early osteoarthritis?

Sometimes, knee crepitus may be an early sign of patellofemoral osteoarthritis. Research by Pazzinatto suggests crepitus can be the first symptom, even before pain starts.

So, if you’re hearing noises along with pain, swelling, or instability, it’s worth getting checked. At Jersey Sports & Spinal Clinic, we can assess whether your symptoms are normal or need further care.

🧪 Ongoing research

Trusted colleagues at La Trobe University are actively studying noisy knees. Read more here. We also highly recommend the excellent work of Claire Robertson, a leading specialist in patellofemoral pain who has even visited JSSC to deliver her training course.

You can find her detailed insights on noisy knees in this great post.

📍 Final thoughts

If your knee makes noise but doesn’t hurt, swell, or limit you, it’s likely physiological crepitus — completely normal and nothing to worry about.

But if you’re unsure, or have concerns about other symptoms, don’t ignore them. Our experienced physiotherapy team at Jersey Sports & Spinal Clinic can help you understand what’s going on and guide you toward the right plan.

👉 Click here to book your assessment today

Noisy knees? No problem — we’ve heard it all before.