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Why do why joints crack?

Published: February 7, 2020

Almost on a daily basis we as physiotherapists encounter people who are concerned about the clicking, popping or cracking their joints are making.  The noises you may be hearing are referred to as joint crepitus, the knee joint being the most common area of concern. However, the spine (neck, mid and lower back), fingers, shoulders and ankles are other ‘noisy’ joints.


It’s important to understand that the majority of the time these noises are not associated with pathology or injury and may actually be indicative of a healthy, properly functioning joint. Interestingly, a person’s beliefs about what these noises can create problems as an individual may modify their behaviour. For example, a person may not squat as deep, lean to one side to prevent the onset of knee crepitus or even stop exercising altogether. This can cause changes in movement patterns, potentially creating imbalances, overuse injuries or predisposing an individual to other injuries. So the importance of understanding crepitus cannot be underestimated.


So what’s that sound?

Most of the time air bubbles forming within the joint space create these noises. This noise occurs at joints where there is a layer of fluid separating the two bones. The space between these joints can be increased through natural everyday movements, or deliberately, such as at the hands of a physiotherapist or other health professional. When this happens, the low pressure in the joint space causes gases within the synovial fluid (the natural lubricant in the joint) to form a gas cavity or air bubble. It can take awhile for this gas to accumulate again which is why most people cannot continue to crack their joints.  This can be visualized in real-time thanks to Gregory N. Kawchuck et al. (2015) here.


However, sometimes these noises can be created by tendons moving over bony protrusions and then quickly moving back into place creating a snapping sound or sensation. This may become more apparent as we age because tendons and muscles tend to lose elasticity making them stiffer. These noises can be alarming, especially if your joints seldom make them, but rarely are they a sign of something sinister.


Can it cause injury?

Some people believe that regular cracking can lead to pathology such as arthritis. Research has shown that there is no correlation or side effects of consistent joint cracking. One researcher took it even further cracking one hand for 60 years. The x-rays demonstrated no sign of any disease and no differences between the cracked and non-cracked hand.

However, if your cracking or popping elicits pain, a reduction in joint range of motion or function then this may be of a concern and you should consult a physiotherapist.

If you are unsure about your joint health and would like to have your noisy joint assessed, book in to see a Physiotherapist or Exercise Scientist at Back in Motion Aspendale Gardens.