Why Do Knees Crack, Pop, or Grind?

Why Do Knees Crack, Pop, or Grind?

Have you ever bent your knee and heard:

• A pop
• A crack
• A grinding sound
• Or a clicking sensation

It can be unsettling especially if you already have arthritis.

So what does it actually mean?

The Medical Term: Crepitus

The sound or sensation of cracking or grinding in a joint is called crepitus.

It’s extremely common especially as we age.

And most of the time, it’s not dangerous.

Why Knees Make Noise

There are several common reasons:

1️⃣ Gas Bubbles Releasing

Small gas bubbles naturally form in joint fluid. When they release, you may hear a popping sound similar to cracking knuckles.

This is harmless.

2️⃣ Tendons or Ligaments Moving

As you bend and straighten your knee, tendons may shift slightly over bone, creating a snapping or clicking sensation.

This is usually normal.

3️⃣ Cartilage Changes

With arthritis, cartilage becomes thinner and surfaces less smooth. When joint surfaces move against each other, it can create a grinding or crunching sensation.

This sounds alarming, but noise alone doesn’t determine severity.

When Noise Is NOT a Problem

Knee sounds are typically not concerning when:

• There’s no swelling
• There’s no sharp pain
• The knee feels stable
• Movement isn’t limited

Many people have noisy knees without major functional issues.

When It Should Be Evaluated

You may want further evaluation if noise is accompanied by:

• Sharp or catching pain
• Locking sensation
• Swelling
• Instability
• Sudden change after injury

It’s the combination of sound and symptoms that matters.

The Important Truth

Noisy knees do not automatically mean:

• You’re “bone-on-bone”
• Surgery is needed
• The joint is rapidly deteriorating

Sound alone is rarely the deciding factor.

Function and pain levels matter far more than noise.

The Takeaway

Knees crack and pop for many reasons most of them harmless.

If the sounds are paired with increasing pain or instability, that’s when it’s worth understanding what’s happening inside the joint.

At Buffalo Arthritis & Joint Pain Center, we help patients explore non-surgical options designed to improve mobility and reduce discomfort so daily movement feels smoother and more confident.

👉 Noisy doesn’t always mean damaged.

‍