Does your knee make noise (e.g. crack, pop etc.) when you straighten your knees, during walking or when you perform squatting-like exercises? Keep reading to learn about normal and abnormal joint noises and what action you need to take if you have signs of knee disorder.

Joint cracking or popping is a common symptom leading to anxiety and clinic visits (Strayhorn et al, 2018). People describe these noises as popping, grinding, cracking, clicking etc. and collectively, these sounds are referred to as crepitus. Is crepitus a sign that there is something wrong with your joints?  

There is a Clear Difference Between Normal and Unhealthy Joint Noises

As mentioned, it is common to hear cracking in knees during bending or straightening movements or during squatting-like exercises. Normal noises are not accompanied by pain, by swelling, warmth or history of previous injury to the knee (Stayhorn et a, 2018). Moreover, normal joint noises are intermittent. In other words, noises that are benign are not constantly reproducible. There is no association between normal crepitus and knee disease. These noises are harmless and therefore should not worry you or affect your function.

Abnormal Joint Noises are a Signal that you Need to See your Doctor

Abnormal noises are accompanied by pain, swelling and possible history of trauma. Unhealthy noises can be reproduced continuously and not sporadic in nature. Moreover, abnormal noises tend to get worse over time and have a higher frequency (Song, 2018).

Knee Joint Cracking can Lead to Fear and Anxiety

Joint crepitus is associated with negative beliefs and altered movement patterns. Individuals with crepitus have a wrong perception of their knee health. For example, a study of 584 individuals living with knee osteoarthritis found that those who have knee crepitus report lower general function, lower knee function and lower quality of life (Strayhorn et al, 2018). However, these differences were not seen objectively. For clinicians, it is important to communicate with patients, reassure them that crepitus can be normal (see above). It is also important to communicate to patients with osteoarthritis that crepitus alone does not lead to loss of function or knee joint deterioration. As crepitus can lead to anxiety, fear and insecurity, a dialogue with your patient can reduce these fears.

Why do normal joints pop?

A study at the University of Alberta’s Faculty of Rehabilitation Medicine led by Kawchuk et al found direct evidence by using magnetic resonance imaging (MRI) that joint cracking is related to cavity formation. The process is called tribonucleation, whereby opposing surfaces resist separation until a critical point is reached. When the critical point is reached, these opposing surfaces separate rapidly, creating a sustained gas cavity. This leads to pressure differences in joints leading to formation of tiny gas bubbles. The relatively quick formation of these gas bubble leads to a pop sound. As you can see these gas bubbles form randomly and hence joint noises that are normal in nature tend to be also sporadic and not constant.

Treatment for Joint Noises

So, if your knee pops, but you also have pain and/or swelling in your knees, or history of trauma or decreased function;  it’s time to see your physiotherapist or doctor to rule out knee pathology and get started with your self-care program. Your physiotherapist will perform a thorough examination of your knee and surrounding joints and function and develop a program that is specific to your goals.

Normal joint noises usually do not require any treatment. If the joint noises are abnormal (see above) coordinate your treatment with your healthcare professional. Strengthening exercises for the quadriceps muscle group might help reduce joint crepitus (Song et al, 2018). Treating muscle imbalances around your knee will provide better stability and lead to better function and endurance in your knees.

References

Lo, G. H., Strayhorn, M. T., Driban, J. B., Price, L. L., Eaton, C. B., & Mcalindon, T. E. (2018). Subjective crepitus as a risk factor for incident symptomatic knee osteoarthritis: data from the osteoarthritis initiative. Arthritis care & research, 70(1), 53-60.

Kawchuk GN, Fryer J, Jaremko JL, Zeng H, Rowe L, Thompson R. Real-time visualization of joint cavitation. PLoS One. 2015;10(4):e0119470.

Sang Jun Song, M. C. (2018). Noise around the Knee. Clinics in Orthopedic Surgery, 1-8.