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Ask a PT: Why do my joints pop and crack when I move?

Joint crepitation or “popping and cracking” can cause a lot of worry in our patients and may lead to negative health beliefs concerning the crepitations. This is a very common question in our clinics and this blog aims to put an end to the negative health beliefs and reassure our patients that what they are hearing and experiencing is normal as well as explain what is actually happening to make that sensation.

What does the research say about joint crepitation?

To this day, there has been no research that has connected a definitive link in between joint crepitus and pathology. According to McCoy et al. 1987, 99% of a cohort demonstrated knee joint crepitus with no reports of knee pain. Another study examined the idea behind habitual knuckle cracking leading to arthritis and found no evidence of a statistically significant correlation. (Castellanos & Axelrod. 1990)

What is actually causing the noise?

There are a couple of theories as to what is causing the joint popping and cracking. One of these theories is that it is due tendons snapping over bony protuberances. Another theory is that inside the joints of our body when the bones move on one another, they can create a vacuum that causes a collapse of gas bubbles within the synovial fluid. This can be compared to the sound you hear when opening a jar of jelly and the pressurized air making the popping noise. When it comes to the knee, one of the most common joints to have crepitus, there is believed to be a slip-stick phenomenon; where the movement of the kneecap and femur move on one another and produce vibrational signals. 

When should I be concerned about the joint noises?

We certainly understand that joint noise can seem scary, but oftentimes joint crepitus should only be a cause for concern if: there is a sharp pain concordant with the joint crepitation or if you feel the joint has suddenly become less mobile secondary to a joint noise. 

Changing the narrative

We have all heard stories of being told that you are going to wear your knees out or thought “I’m too young for this” or “you need to get that checked out,” but these thoughts need to begin to reflect what the evidence states about joint noise. These thoughts can have a negative effect on our health and lead to us being fearful of moving and take away some of our cherished activities. As you can see by some of the research, having joint cracking and popping is a completely normal sensation and should not cause you to stop your physical activity or believe you are damaging your joints. If anything, having joint crepitus is a sign of having healthy and lubricated joints full of synovial fluid, which is great! 

If your joint noise has you feeling uneasy, then please make a visit with your local Therapydia physical therapist, but we hope this blog will help you feel more comfortable with some of those noises you have been experiencing and be the motivation to get you more active again. 

Jessica Jones

Physical Therapist

Jessica recently moved to Seattle from Boston, MA and is excited to join the Therapydia team. Her treatment experience includes orthopedics, sports medicine, pediatrics, and vestibular therapy. Jessica received her Doctorate in Physical Therapy from Northeastern University in Boston, MA in 2016. She has completed the Pediatric Physical Therapy Residency at Boston Children’s Hospital and is in the process of completing a Comprehensive Vestibular Rehabilitation certification. Jessica believes in empowering and inspiring patients to take control of their health through education, movement, and exercise. She enjoys treating patients of all ages and levels while utilizing soft tissue techniques, neuromuscular re-education, balance training as well as therapeutic exercise. In her free time, Jessica enjoys yoga, dancing, kayaking, and hiking with her dog!


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