The few studies completed to date have examined how stem cells heal traumatic injuries rather than degenerative conditions such as arthritis. Results have been promising but, as Einhorn points out, the required repair mechanisms in each circumstance are very different.
Another downside is cost: The injections aren't approved by the FDA, which means they aren't covered by insurance. At $4,000 a pop -- all out of pocket -- they certainly aren't cheap, and many patients require more than one shot.
Ironically, one thing driving up the price is FDA involvement. Two years ago, the agency stepped in and stopped physicians from intensifying stem cells in the lab for several days before putting them back into the patient. This means all procedures must be done on the same day, no stem cells may be preserved and many of the more expensive aspects of the treatment must be repeated each time.
Centeno says same day treatments often aren't as effective, either.
But despite the sky-high price tag and lack of evidence, patients like Beals believe the treatment is nothing short of a miracle. She advises anyone who is a candidate for joint replacement to consider stem cells first.
"Open your mind up and step into it," she says. "Do it. It's so effective. It's the future and it works."