By Sophie Dean and Sam Millard, 5th April 2017.

One of the most common questions we get asked is, “what’s that cracking sound?”

The “cracking” or “cavitation” of a joint occurs when a joint is separated. The separation of the joint reduces the pressure in the joint from which some of the naturally occurring gases in the fluid of joints leave the joint, creating a bubble which then collaspes on itself creating a “pop” or “crack”.

Usually this question is followed by another question. “Does that cracking cause arthritis?” A recent study (1) found “in these cohorts of persons aged 50 to 89 years, a history of habitual knuckle cracking – including the total duration and total cumulative exposure to knuckle cracking – does not seem to be a risk factor for hand Osteo Arthritis.”

There are many proposed mechanisms as to why we do this. Some suggest it is to reduced the perceived stiffness whilst others suggest is has an effect on the brain to help us concentrate, the same way as a child with ADHD will fidget to aid concentration. Whatever the reason for the habit, it doesn’t seem to cause us any problems.

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References:

1. deWeber K, Olszewski M, Ortolano R. Knuckle Cracking and Hand Osteoarthritis. Journal of the American Board of Family Medicine 24 (2): 169-174 (2011)