You might crack your knuckles by pulling the tip of each finger, make a fist or bending your fingers backwards. And if you do one of these things, its more than likely the person sitting next to you is wincing, or has said that cracking your hands will give you arthritis…
So what makes that cracking sound?
Some of the joints in your body (including those in the hand), have small spaces between the two bones which are filled with synovial fluid which helps to lubricate and cushion the joint.
When you ‘crack’ your knuckles, the space between the two bones increases. This creates a negative pressure, which draws the synovial fluid into the newly created space. This movement of fluid creates the popping sound you can hear and feel.
For a long time, it has been suggested that cracking your knuckles could lead to an increase in the risk of developing arthritis down the track. One Doctor by the name of Donald Unger even conducted his own research, which included himself as the only subject. Over 60 years he cracked the knuckles on his left hand at least twice a day, while not cracking the knuckles on his right hand. He concluded that neither hand showed any sign of arthritis.
There are limited studies which investigate this particular question. The most recent and comprehensive study yet assessed radiographs of people aged between 50 and 89 years old, according to the frequency of knuckle-cracking behaviour. The Study suggests that habitual knuckle cracking does not appear to increase your risk in developing osteoarthritis in the hand.
So, it appears that the biggest consequence of knuckle cracking would appear to be its annoying effect on the company you keep!