One researcher, Dr Donald Unger, actually cracked the knuckles of his left hand at least twice a day for over 50 years whilst never cracking those on his right hand in order to prove his mother wrong – he never developed arthritis in either hand, and won a Nobel award for his efforts in 2009. Of course, one person’s story isn’t enough. However, even more scientific studies haven’t shown any link at all between knuckle cracking and arthritis.
But that doesn’t mean that you can necessarily crack away with no regard for your joints – some radiologists think that there is some visible damage on X-rays to knuckle joints caused by continuous cracking of them, and those who crack their knuckles habitually did, in one study, seem to have weaker hand grip – but it’s not entirely clear that it was the knuckle cracking itself that was the cause of it.
Whatever the results of it, the noise that puts so many people’s teeth on edge is not bones rubbing together, or even (except in rare cases) tendons slipping over bones, it’s actually caused by joints being pulled apart slightly, reducing the pressure in the fluid between them, and causing gases dissolved in the fluid to form bubbles which then burst (a process known as cavitation) – which is what the ‘crack’ sound is. It takes about 20-30 minutes for these gases to redissolve in your joint fluid, meaning that you can’t crack your knuckles again for another half hour!