Actually my last stem cell treatment a few years ago was done for both the left knee cartilage and left hip cartilage at the same appointment. The regenerative physician just withdrew enough blood to spin down for an ample amount of PRP (plasma Rich platelets). To re-inject into the joints. They combined the PRP with hyaluronic acid. They also did a local anesthesia to the area prior to the injection.
Do realize there must be enough cartilage left in the joint to build more cartilage in.

I have read that there is a trial of a “scaffolding@ with cells grown upon it then implanted, but I’m unsure where this is taking place.