"Many people have become captivated by the idea of using stem cells to fix their damaged joints, and some claim to have been helped."

"But there is no clear evidence that these treatments work, and their safety has yet to be established. Most researchers, including those at the National Institutes of Health, think that efforts to sell therapies involving adult stem cells, which can develop into different types of cells to replenish tissue, have gotten way ahead of the science. Even so, hundreds of clinics have popped up around the country to meet the demand. Some of the clinics also inject joints with platelet-rich plasma, a solution of platelets extracted from the patient’s own blood.... There is almost no regulatory oversight of orthopedic procedures using bone-marrow extracts or platelets, which are regarded as low risk.... 'I believe strongly that it isn’t ethical to charge patients for unproven therapies like these and raise what are likely to be false hopes,' said Paul S. Knoepfler, a stem cell researcher at the University of California, Davis. He said that some properly conducted studies on platelet-rich plasma suggested it might help, but others did not. As for stem cells extracted from bone marrow, Dr. Knoepfler said well-controlled studies were even scarcer, also with mixed results.... [P]atients rely on testimonials and other informal evidence.... 'The power of anecdotes is just amazing when it just catches on,' said Donna Messner, the president of the Center for Medical Technology Policy, a nonprofit research group. 'This is how snake oil has been sold for generations.'"

From "Stem Cell Treatments Flourish With Little Evidence That They Work/The F.D.A. has taken an industry-friendly approach toward companies using unproven cell cocktails to treat people desperate for relief from aging or damaged joints" (NYT).