I've done alot of research on this one and from what I"m seeing its a 50/50 chance that it works. I am a candidate for one but refuse to do it, I'm also a chicken when it comes to large needles in small places.
Something I have been trying now that has been recommened by the Arthritis Organization in a recent issue of their magazine is 1200 mg of Vitamin C. According to some studies they did it actually reduced the degeneration time of the knee by 50%.
You might be able to find that same info on their web site. I figured since it is passed through the system and not stored it certainly can't hurt to try.