I wish I could give you a better answer, West. But any benefit of spinning down a patient's blood, extracting the platelet fraction, and then injecting the platelet-rich plasma into injured joint areas is BASED ON FAITH that the platelet fraction will be "contaminated" with rare undifferentiated stem cells, that these cells will then differentate into cells that will replace the damaged cells, such as cartilage cells, muscle cells, etc. It is purely a theory based on some basic science, and the evidence of it actually being effective clinically is anecdotal and not based on actual observations of cellular differentiation and healing in these patients. That doesn't mean it is not happening, but it is truly a treatment of faith at this point.
The claims of it being effective are based on patients' subjective sense of improvement and on objective evidence of healing, like reduced markers of inflammation. But the healing may have happened anyway, and the placebo effect of wishful thinking, confidence in the theory, and spending a boatload of money by these patients is not, or cannot, be controlled out of the studies. In otherwords, the process and expense and small numbers of patients doing this completely precludes the possibility of studies that are double-blind and controlled. That does not mean it doesn't work. But if you wish for something hard enough and spend enough of your own money on it, you can will yourself into believing you are better, and that can actually make you better. If you believe it, you lose some of the protective effects of "guarding" and allow yourself to increase your range of motion in exercizes, which might be beneficial all by itself. Belief that something is helping is a powerful force, which is why placebo-controlled and double-blind studies are necessary. When you believe in something and have confidence, it reduces steroid secretion, and that allows certain immune functions to improve. That is why this is not an approved procedure here. The fact that patients have to fly off to Germany to get this treatment at private centers that are more than willing to take the money should say something. It could take a number of years before there is an actual answer. It may be just a craze among rich athletes. But personally, I am 100% certain that medical scientists will be perfecting the ability to re-capture the totipotentiality of stem cells, and that the future is bright as far as injecting these cells into damaged tissue to re-create healthy tissues, including neuronal tissues in injured brains. I think we are on the verge of a revolution in medical treatments from this. Science is good.
I hope that helps and does not just cloud the issue further.