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"Mechanically, it works fine -- it's just the pain is starting to be unbearable," Landis recently told the Atlanta Journal-Constitution.
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 down.
"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."