This is a better article:
http://www.aaos.org/news/aaosnow/sep10/clinical1.asp
There are different kinds of PRP. NRH sports clinic doctors can tell you if you are a candidate. I had lots of arthritis and swelling, problems walking and with stairs. I had meniscus surgery and my knee never improved after, even with PT. Swollen knee which made my kneecap not track properly. I was facing a knee replacement, but I believed at 50, I was too young and gaining weight.
Now I can kneel, go up and down stairs, bend down, etc. No pain, little swelling. I can't jump off metro buses, but I don't think about my knee every single minute. $1300 - not covered by insurance. Worth it. I will need a knee replacement, but I have been pain-free for 3 years. And yes, I had cortisone and synvisc before. They work also, but this has been more lasting.