Jerry Wade used to love bird-watching with his wife, an avid birder.
"I'm not a birder myself, but I like being active and getting out there
with her," he says. "Bird-watching puts you into natural areas and some
rough terrain -- it's not an easy physical activity."
But in the fall of 2005, the 66-year-old Columbia, Mo., resident, who had
retired in 2000 from a career in community development, started noticing
"pains and twinges" in his knees. A visit to his doctor in January 2006