I am with Ollinger. I don't think style will solve your problem. Even if you play a 'low impact' style you will have occasions where you quite naturally go with full exertion..
I don't care if you are playing doubles with seniors - those guys are going to expect you to run that lob down since you are still young.
Limit your tennis to 1 match a week for a season.. Because if you push it too much you are going to have to give up tennis. It sounds like your Doc wants to you to quit already.
Do the rehab and whatever other exercises you can find that help your injury religiously. And personally though its quackish I know I would take both fish oil and a joint supplement..