hi; had bad knees for years, reduced my riding in 2018 to 5 miles, right knee surgery 2019, down to 3 miles maybe 3 -4 times week, 2020 left knee surgery, same old story. in jan and feb 21 [@76 hard to face the cold!]. i tried some 5mile runs, which resulted in knee flareups lasting a week. meanwhile i put together a 1x10 from a miele toscana frame i had hanging on the wall. previously i was running 3x9 mtb gears to keep the knee load low. 36 upfront 11-40 in the rear, i am still working on the gearing, i have a 11-36 coming and may try a 38 upfront as i seem to be over geared for uphills and under geared for downhills. put the bike together with china parts, runs well for the moment. how long the components or i last on a bike is debatable. just did a 5 mile run, now wait and see what the knees say.