In every issue of WebMD the Magazine, we ask experts to answer readers' questions about a wide range of topics, including some of the oldest -- and most cherished -- medical myths out there. For our October 2011 issue, we asked Dimitrios Pappas, MD, assistant professor of medicine at Columbia University's College of Physicians and Surgeons, about the long-term effects of one popular childhood activity: knuckle cracking.
Q: My 10-year-old son cracks his knuckles. Is it true that it causes arthritis?
There is no specific test to diagnose ankylosing spondylitis, but imaging by X-ray and MRI may show evidence of inflammation of the sacroiliac joint between the sacrum (the triangular bone at the lowest part of the back) and the ilium (the bone felt on the upper part of the hip). Some symptoms may include:
Inflammatory back pain (gradual in onset, lasting over three months, with stiffness and pain that is worse in the morning and improved with movement)
Reduced mobility of the spine
Ten-year-old boys love to make noises with their body, so it's not surprising your son is intrigued with the sound of a good knuckle pop. But you can put your fears aside -- the idea that knuckle cracking leads to arthritis is FALSE.
"There have been a few studies on this,” Pappas says. "None of them shows any change in the occurrence of arthritis between people who habitually crack their knuckles and those who do not.”
But here's something cool you can tell your son: The "pop” that comes when you compress your knuckles isn't from bone snapping on bone. It happens because, as the bones are stretched apart, a gas bubble forms and then pops.
While such joint cracking doesn't lead to arthritis, medical journals do contain reports of people who injured their ligaments while cracking their knuckles. At least one study also found the grip of people who habitually crack their knuckles may weaken over the years.