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?
"Mechanically, it works fine -- it's just the pain is starting to be
unbearable," Landis recently told the Atlanta
That pain is the result of osteonecrosis -- also known as avascular necrosis
(AVN). It's the same condition that disrupted the career of baseball and
football star Bo Jackson.
What Is Osteonecrosis?
Osteonecrosis develops when blood vessels that feed bones are injured,
destroyed, or blocked. This causes a lack of blood circulation to the bone,
which can lead to bone death. In Landis' case, the damage reportedly occurred
in conjunction with a hip fracture he suffered in 2003.
"When you are young and strong it takes a powerful force to cause a hip
to break. And because of that, often key blood vessels in the area can be
injured as well," says James Urbaniak, MD, professor of orthopaedics at
Duke University Medical Center in North Carolina.
While doctors say some patients may generate new blood vessels to resupply
the area naturally, when that doesn't happen, bone can quickly begin to break
"Without adequate circulation, the bone simply begins to crumble and
die," says Michael Bronson, MD, chief of joint replacement surgery at the
Mount Sinai School of Medicine in New York City.
Moving Painfully With Osteonecrosis
In Landis' case, problems were complicated further since the area normally
fed by the injured vessels was the femoral head, or tip of the thigh bone,
which sits directly inside the hip socket.
"So now, instead of having a smooth, spherical shape to the end of that
bone, allowing it to move freely inside the socket, it begins to crumble, and
becomes irregularly shaped," says Bronson.
As a result, he says movement becomes like "trying to put a square peg
in a round hole."