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Why Do Joints Pop?

A very common complaint I hear from people who I see is: "My knee pops or cracks when I squat. Is that normal?"

The short answer is yes, it is normal, as long as it is not associated with any pain. The simplest explanation for this is that as we get older, our joints simply do not move like they did when we were 15. Muscles get tight, joints get stiff, we have past injuries that have changed the way our body moves. However, if every time you hear a "pop" and it is accompanied by pain, that is when we as physical therapists need to take a closer look.

The "popping" or "cracking" you here has a fancy name for it: cavitation. All of our synovial joints (joints that allow for movement) are surrounded by a joint capsule that contains fluid (named synovial fluid). When there is a change in pressure between the synovial fluid and the gases in that fluid, we get what is called a "cavity formation," which is the sounds that we here.

Now, there are other noises that may indicate something may need to be checked out:

click - clicks can also be unbothersome, but sometimes they do cause pain. Often times, clicks occur due to tendons or ligaments not being perfectly aligned, or even a nerve that might not be moving as smoothly over a bony prominence as usual.

ripping/tearing - very common, especially in the knee. If we have had past injuries or trauma to the area, we have had scar tissue that has built up in that area. Often, the ripping/tearing sensation is from scar tissue being broken up, which isn't necessarily a bad thing. However, again if it is accompanied by pain or swelling, further testing should be done to rule out anything potentially wrong.

The most important thing to remember as we get older is that motion is lotion. To put it simply, our joints LOVE movement. They crave it, seek it out, want it all the time. In our Western society, we are sitting constantly which causes all of our joints, muscles, tendons, and ligaments to stay in one position for a heck of a lot longer than it should. They don't like that and they will let you know about it. The more we move, the better our bodies will feel.

In conclusion, joint noises are almost 95% always normal and I would say 100% normal if not accompanied by pain. I'm a PT and every time I pull my shoulders back into good posture I hear crackling in my shoulder blades and spine. Completely normal. If, however, you get some pain when you hear a pop or click, make sure you see your local PT to get it checked out.

And remember, keep moving!

James Caldwell PT, DPT


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