Think Dra Justina Lopez primarily uses stems cells, and have heard good success for knees, especially. Her number is 376-766-5563.
Regarding PRP's , which is totally different from stem cell therapy, I had it done in my back about 8 yrs ago and it bought me about 3-4 months of comfort and that was about it. It was with a doctor in Guad, at Salutaris Medical Center, but I would not recommend him.
However, he did not use any imaging or fluoroscope, which I think would have a higher success rate. My sister had that type of PRP for torn miniscus up in the States and it has really worked for her. So, I think a targeted use of PRP with the above mentioned targeting tools might work better.