Someone who knows more than me

I am 45 and have abused my knees for the past 25 yrs. I was one of the top ranked Body Builders in the Rocky Mnt. region of the U.S.A. In addition to all of the heavy weight training that goes with this sport(knee damage) I am very bowlegged. There have been 6 knee surgeries between the two knees(ACL, meniscus tears, cartridge damage, debriment...) 2 surgeries ago(double knee surgery) I was told I have OA(Stage 3) mainly in the knee caps. This past surgery(1 week ago on left knee) I was told the OA was going up into the thigh bone. So much for the damage...where do I go from here? I was told by OS that there should be no more weighted leg training(squats, presses, leg extensions, etc.). OS says I am on my way to TNR. Unfortunately I have found in the past, the stronger I keep my legs the less problems I have. I have been trying to come up with some kind of a strength training program for the stationary bike. Maybe someone out there knows of one or perhaps another type of approach to strength training of the legs. Next question? What to do about this incessant crunching in the center of the knee. Feels like someone poured a cup of gravel into the knee when I walk. The knee mainly grinds and crunches while walking on level surface, not while going up or down stairs. Even though there is sufficient pain associated with it, the crunching and grinding is primary, it gives me the creeps . I have tried condroiton, glucosimine, MSM, heavy water intake, anti-inf, COX inhibitors, ice, heat... Thank you for taking time to read and hopefully answer this. Hope all of you are finding answers for this curve in life we have all been thrown.