At 55, George Chung of Los Angeles could keep up with skiers decades younger, taking on difficult slopes for hours and hours. "Skiing was my passion," he says.
Then the pain started, and the bad news. He had severe osteoarthritis, the ''wear-and-tear'' type, in both knees. Doctors suggested surgery, but he chose instead an investigational treatment -- injections of stem cells. Two months after the first treatment, he was out of pain. "I had been in pain of various degrees for 6 years," he says.
Now, nine treatments and 3 years later, he is back to intense skiing. Last year, he also took up long-distance cycling, completed five double-century cycling rides, and earned the prestigious California Triple Crown cycling award.
Treatments with stem cells -- which can grow into different types of cells -- are booming in the U.S., with an estimated 500 or more clinics in operation. Some clinics offer treatment for conditions ranging from autism to multiple sclerosis to erectile dysfunction, often without scientific evidence to support how well they work.