A popular factoid, often told to those who like to crack their knuckles, is that cracking your knuckles repeatedly will cause arthritis years down the road. Is there any truth or scientific backing to this claim? Are you potentially risking your joint and finger mobility?
Does Cracking Your Knuckles Increase The Risk Of Arthritis?
The short, simple answer is ‘no’. There is no current scientific evidence which backs up the claim. Quite the contrary. The most recent study examined the hand radiographs of 215 people (50 to 89 years of age) and compared them. They compared the sets of those who habitually cracked their knuckles to those who did not and found that knuckle-cracking did not cause hand osteoarthritis, no matter how often or for how long a person had cracked their knuckles.
This does not mean knuckle-cracking is perfectly safe, however. Another study concluded that while there was no increased risk of arthritis in the hands of chronic knuckle-crackers, people who regularly cracked their knuckles were more likely to experience hand and finger swelling due to inflammation and up to a 25% reduction in their grip strength.
So what does cause arthritis then? There are many different kinds of arthritis, over 100 different types have been identified so far. The most common among them, osteoarthritis, is caused by simple age and genetics. If you X-ray the hands of people age 65 or older, 70% will have arthritis, with the osteoarthritis tending to be worse in the dominant hand. Since there are many knuckle crackers within that 70%, they may mistakenly believe it was caused by their habit.
Where Does The ‘Popping’ Or ‘Cracking’ Sound Come From?
Synovial fluid (a viscous, non-Newtonian fluid found in the joints and acts as a lubricant) has dissolved oxygen, nitrogen, and carbon dioxide within it. When pressure is applied to a joint, the area inside the joint capsule expands. However, the expansion is limited by how much fluid is contained in the joint. At some point, the pressure becomes too much and the cracking sound you hear comes from the dissolved gases rapidly being released from the synovial fluid.
Castellanos J. Axelrod D. “Effect of habitual knuckle cracking on hand function.” Annals of the Rheumatic Diseases. 49(5):308-9
Mirsky, Steve (2009). “Crack Research: Good news about knuckle cracking.“. Scientific American.
Brodeur R: “The audible release associated with joint manipulation.” Journal of Manipulative & Physiological Therapeutics. 18(3):155-64