Hi Canadian-Ice,
You are right in that the one thing that all PRP studies end with is that not enough is yet known about dosage, number of injections, etc; so there is a lot of variety in how docs approach it. The two things that most of the studies agree on is that their does not appear to be any downside unlike cortisone, and that 60 to 80 % of patients show minor to major improvement.
You mentioned wondering whether any anti-inflammatories might have been included in your injection. This would be highly unlikely, since it would totally counteract the healing cascade affects of the PRP. Most docs will ask you to even stay off of oral anti-inflammatories for at least a couple of week after the injections. It is possible that your doc included a mild pain killer in the injection, as ours did with this last round, making the first day or so much more comfortable.
As for your knee, when I had my hip injected last fall, my wife decided to have her knee that suffers from occasional chondro-malacia injected, and she swears that she got through the ski season better than in previous years. Last week she decided that she was impressed enough to have both knees injected when I went in for another hip injection.
People have to remember that PRP injections are not intended to make you feel better right away; in fact the intent is to set up a healing response in the area, which may be uncomfortable at first. The biggest news is the recent MRI study out of HSS in New York, that in a blind study showed that there was no progression in arthritis out to at least one year after PRP, when they would have expected around a 5% cartilage loss in an arthritic joint during that time.
Someone mentioned Durolane which is a viscosupplement injection that I had pretty good success with a couple of years ago. It is interesting to note that some studies with PRP show that one of its many affects along with stimulating a healing response can be to stimulate the production of healthy joint lubrication, similar to the longer term affects of the viscosupplements. Since the PRP also offers the hope of overall healing and cartilage protection, I think that I would not go back to a viscosupplement again at this point.
Good luck with keeping all of our parts working