My idea of fastpacking is to take a daypack and pay someone to transport the main luggage betwen B&Bs Off to run Anglesey then Bangor to Borth at the end of this week in my mission to run round Wales (Pembs, Ceredigion and Offa's paths already done). Contours is handling the packing and I'll see to the fast
I don't want to put a damper on things, but I'd say beware of trawling opinions until you get the one you want to hear. Depending on how much cartilege was removed, it could be like driving a car on a rim - you only see that in USA's dumbest traffic-cop youtube clips, right?
It's important to keep up physical activity, perhaps to be ready for that day when a surgical solution is offered, but at least for yourself to keep fit and healthy. Moderate exercise every week without impact on that joint, and also some strength training could be the thing, like the doc says. Can you convert it to an opportunity to finally learn how to swim - join a class?
You might like to read some American guidelines on exercise and arthritis pdf here. NB I am no kind of medical practitioner.