Dr Margaret answers emailers’ embarrassing problems
in this monthly problem page.

Cracking knuckles

Dear Dr Margaret
I crack my knuckles a lot. I don’t know why I do it. It annoys my mother, and she says I will get arthritis in my hands. Is that true?

I have noticed a lot of people cracking their knuckles recently, and I wonder if the habit is becoming more common. Although it seems reasonable to worry about it, arthritis may not actually be a risk.

How the cracking noise occurs

Exactly how the cracking noise occurs is a bit of a mystery, but scientists think it is probably caused by the release of bubbles in the fluid surrounding the joints. Each joint is contained in a small bag of special fluid (the ‘synovial fluid’). When you stretch or pull your joint to ‘crack’ it, you are stretching the bag of fluid, and this lowers the pressure in the fluid. As a result, a bubble of carbon dioxide gas is released inside the bag. This makes the cracking noise. It takes 10–15 minutes for the carbon dioxide to redissolve into the fluid, which is why you cannot crack your knuckles again immediately.

Arthritis probably not a risk

There has not been much research on the risk of arthritis from this habit. One survey of 300 people identified 74 habitual knuckle-crackers over the age of 45 (so it was assumed they had been doing it for years). Their joints were no more damaged than the joints of people who never cracked their knuckles.

This ties in with the experience of an American doctor who wrote in a medical journal that he had cracked the knuckles of his left hand, but never the right, for 50 years. He thought it would be interesting to compare the degree of arthritis in his right and left hands, and there was no difference.

However, the survey of knuckle-crackers did find that they had somewhat lower grip strength, and their hands were more likely to be slightly swollen. There have also been reports of hand injuries from what their doctors described as ‘the forceful manipulation needed to achieve the audible pop’.

Stopping the habit

Do you want to stop cracking your knuckles? If so, you could try the ‘competing response/habit reversal’ method that I described a week or two ago when I was discussing nail-biting. I think it might also work for knuckle cracking. It simply means that whenever you feel the urge to crack your knuckles, you do another action instead. For example, you could wear an elastic wristband, and snap it on the inside of your wrist whenever you feel the urge to crack your knuckles. Alternatively, clench your fists tightly with the thumbs inside against the palms of your hands for 1 or 2 minutes; if you are in a situation where this action would be inappropriate, grasp some object instead.

Sources of information

Bunger D. Does knuckle cracking lead to osteoarthritis of the finger? Arthritis and Rheumatism 1998;41:949–50.

Castellanos J, Axelrod D. Effect of habitual knuckle cracking on hand function. Annals of the Rheumatic Diseases 1990;49:308–9.

Chan PS, Steinberg DR, Bozentka DJ. American Journal of Orthopedics 199;28:113–4.

McCrory P. All cracked up. British Journal of Sports Medicine 2003;37:377.

Wild E. You should know, you’re a medic – do people who crack their knuckles get arthritis? Student British Medical Journal 2001;9:443–86.