First, I'd highly suggest NOT going ahead with the TKR until every other option (both surgical and otherwise) have been tried (not just thought about) and failed. They had contemplated doing a partial knee replacement on me about 2 years ago and opted to try everything else first. Knee replacements don't last forever and each subsequent replacement lasts for a shorter amount of time so for me (at the time I was about 28, now almost 31), they said they'd probably end up doing them at least 3 times in the span of my life, if not more. Not to mention possible revisions, etc.
OATS might be a good place to start but even before that, have they suggested doing any type of ACI surgery where they harvest your own cartilage cells, regrow them in a lab, and then fill the defect with your own cells? They did this for me and it worked and I had about 70% of my cartilage, if not more, under my patella missing. OATS was going to be the second step, if the ACI didn't take, as they prefer to use your own cells first (at least my doc did).
I'd definitely seek a second (or third or fourth) opinion, even if it's just consulting via e-mail with some of the top docs. Where do you live?