Any Thoughts on Stem Cell Treatment for Arthritic Knee?

Hi All: I am curious if anyone has tried stem cell therapy for a bad knee. As I have researched it, this consists of injecting stem cells from the hip into the knee to either help re-grow or otherwise cushion the knee. I have a severely arthritic knee (bone on bone) which dates from having torn cartilage and an operation for it back in the stone age of surgery (1977 when I was 16). I had another operation on it in 1998 and about 3 years ago it seems that all remaining cartilage or any other cushioning disappeared. I tried an injection of synthetic cartilage after this, but it didn't help the situation. I'd like to try all options before thinking about a knee replacement and, from what I read, this treatment seems promising. But it appears to be rather new, so if anyone has tried it with success, I would like to hear about it. I haven't been able to do breaststroke in 3 years, which is kind of a bummer for a life long breaststroker. I was given feet that point out naturally, but a bum knee to go along with them. Please let me know if you've tried this, where you went and what the results have been.