Why Do My Knees Crack?


Patients often describe how their joints especially their knees make a cracking or grinding noise often when they squat or kneel. Understandably they are often concerned and anxious by this. They often ask what does this mean?

In most cases, there is nothing to be concerned about. Joints can make all kinds of noises, from loud popping noises to grating sounds to rubbing sensations. Most of these sounds are described by the term crepitus, which essentially means “joint noise.”

The theory that popping your joints will lead to arthritis holds no truth and has no support in the research literature.

Similar to when you crack your knuckles; loud popping noises from your knees are most likely caused by what is called cavitation. Cavitation results from a change in joint pressure that allows carbon dioxide, which is normally dissolved in your joint fluid—a.k.a. synovial fluid—to come out of the solution and form gas bubbles in the joint. This creates a small cavity in the joint, and when the cavity closes quickly, the bubble essentially “pops” and makes the all too familiar cracking noise.

Most people will notice a grinding noise in the knee joint when they squat. If it’s not painful, there is nothing to be concerned about. Many people experience this throughout their lives and never have any problems.

However if this noise (crunching or clicking) is accompanied by pain, then thats a different situation . You should have your knee examined by your doctor or a Chartered Physiotherapist if you’ve had a trauma which has resulted in you not being able to bear weight through your knee or if your knee locks or gives way or looks deformed.  If this is the case, physiotherapy, or in worst cases, surgery, will be required to resolve the condition to allow you to normal activities.