Have you ever experienced “creaking”, “popping”, or “grinding” at your knees with bending, squatting, or going up/down stairs? We’re often asked in clinic about some “clicking” or “popping” heard at the knees and whether it’s normal, a sign of injury, or even a sign of degeneration. It can be quite a troubling thing if you’re unsure of what it means, and so today I wanted to take some time to try and explain what we know to date and why it might be happening.
This “creaking” type sound that is most commonly heard at the knees is clinically referred to as crepitus. Research on the topic of crepitus is quite slim, but a recent editorial that I’ll try and sum up provides a nice summary of what’s known and the questions that still need answering. On the whole, researchers and clinicians are still on the fence as to what exactly causes crepitus at a joint. One theory is that it may be caused by the movement of the patella (knee cap) over the femur (thigh bone) as it slides within its groove while being compressed by the quadriceps as you bend and straighten your knee. This movement occasionally results in the “pops” you hear and can create vibration, which results in that fine creaky sound. Another theory is that the smooth cartilage surface underneath the knee cap can become grainy and less smooth as a part of normal aging. This in turn results in irregularities along the surface, producing vibrations (creaking) with compression and sliding (bending and extending knee). Again this is a normal part of aging and isn’t the consequence of any degradation at the joint. Lastly, the crepitus could be the result of gas bubbles within the synovial fluid (joint juice) that are compressed creating the “popping” sounds that we hear first thing in the morning or after periods of sitting. Most likely, it’s a combination of the above with other components that haven’t yet been documented or explored.
Looking past the cause, the biggest thing to know about crepitus is that unless it is paired with pain, swelling, or a loss of function, it’s really nothing to worry about. In the minority of cases where it is paired with pain, swelling, or loss of function, a variety of knee problems could be at work (meniscal injuries, osteoarthritis, osteochondral defect…) and should be checked out by the appropriate health care practitioner. However, crepitus on its own is not likely due to any harmful changes at the knee, and is in fact very normal. So if you have a bit of “creaking” or “crunching” in your knees without any of the other symptoms stated above, keep on keeping on and don’t let it limit your activity or keep you from enjoying the things that keep you moving. You’re not doing any harm by keeping active and in fact are probably doing yourself a great favour. If you have any questions about crepitus that you wanted to discuss further, feel free to contact us at email@example.com or book an appointment today.