I’m forever telling people to stop cracking their knuckles. “It will give you arthritis” I helpfully inform. I’ve been a firm believer of this myth for years, and I’ll happily divulge this ‘fact’ to work colleagues, friends or anyone I feel comfortable enough to moan at. But for everyone who stops cracking, another tells me cracking your knuckles does no harm.

Determined to prove myself right, I asked top orthopaedic surgeon Mr Toby Colegate-Stone to fact check this medical myth for me.

What makes that popping sound when you crack your knuckles?

The knuckle joint (otherwise known as the metacarpophalangeal joint) is similar to a ball and socket type of joint. There’s not much of gap between the 2 sides of this joint. Also, the joint moves smoothly because of synovial fluid that fills the remaining space. However, if you extend and detract the space between the 2 sides of your joint (for example, by pulling the ‘knuckle’ apart) a new space is created within that joint that has a negative pressure. This causes bubbles of gasses to form. These bubbles escape to fill the space and then collapse or pop. This is what causes the ‘cracking’ sound.

But is cracking your knuckles actually bad for you?

There have been a few clinical studies looking at the effect of constant ‘knuckle cracking’. They have looked at how it affects various aspects, such as swelling, weakness, how loose the joint is, the range of movement and other specialist hand outcome scores. No significant negative effect was noted on these outcomes in those who ‘knuckle crack’. It may be that those who have already have laxer joints, as assessed by the Beighton score, have the knack to knuckle crack.

Other studies have tried to look at the longer-term effects. However, meaningful outcomes can become difficult to interpret because such studies have so many variations in the people being studied. The main concern for many is whether cracking your knuckles means you will develop osteoarthritis of the joint.

What is osteoarthritis?

Arthritis refers to the process of joint inflammation, which can potentially progress to painful degenerative joint changes. The most common form is osteoarthritis. In this form underlying bone is exposed where the cartilage lining the joint is gradually worn away. This can give rise to further painful change as bone grinds on bone as the joint moves.

Published studies looking at longer-term outcomes haven’t found a meaningful link between the ‘knuckle cracking’ habit and development of arthritis. There perhaps is an association with joint swelling in the longer term, however the cause of this may be independent of the actual act of ‘knuckle cracking’. Indeed such research has not assessed whether habitual crackers have any other habits that may also impact their outcomes. So it appears currently that there is no definitive evidence to suggest that the act of ‘knuckle cracking’ causes significant long term harm, although it might impress or intimidate a few onlookers!

Medical Myth: False

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