The myth that cracking your knuckles will give you arthritis is one of the most common lies told to kids by their parents, up there with "don't do that or you'll go blind" and "your face will get stuck like that".
But this myth has been busted just like the rest, and Dr. Donald Unger even spent over 60 years proving it's not true, cracking only the knuckles in his left hand to compare to the right.
So what actually happens when we crack our knuckles?:
When you make the motion to crack your knuckles—either by stretching your fingers or bending them backwards—you expand the joint. This causes the pressure between the joint to decrease, as well as the ligaments that connect the bones and the joint capsule that holds all of it together. That depressurization causes gasses like carbon dioxide, nitrogen, and oxygen that are dissolved in the synovial fluid to form into little bubbles that rush into the empty space. As the joints settle back into place, the fluid also returns to its rightful place and pops those little bubbles, causing that recognizable cracking sound.
The sensation of cracking your fingers feels good because the stretching of the joint also stimulates nerve endings found along the fingers; joints can’t be cracked more than once within 15 minutes to a half hour, which is about how long it takes for those gasses to dissolve back into your synovial fluid.
Dr. Unger's findings were published in a journal called Arthritis & Rheumatism back in 1998, and yet I still constantly hear parents telling their kids they'll get arthritis if they crack their knuckles. So what's it going to take for this myth to die?
-Via Mental Floss