Even with knee replacements my rheumatoid arthritis slows me down a bit, so I took my cousin's advice to travel Europe with a river cruise. Traveling on the Viking Kara was far more comfortable than I imagined. I didn't feel nearly the pressure to walk and walk to see the sites because I could sit on deck and see so much.
At each stop we could either walk into town or Viking provided buses to enable us to see the sites. There were only two opportunities to explore that felt a little too daunting to go the distance. We had an elevator to access our room, and the stairs up to the upper observation deck were very doable.
The bathroom was also very easy to manage with flexible faucets, ease of use of the shower, commode, etc.
With limited mobility it was very nice to be close to the lobby and deck entrance. Our bed were very comfortable and the bath was surprising manageable. We didn't watch much TV but it was nice to catch the news on the big screen while we were changing and watch a Beatles documentary while we packed. We pulled out of Cologne at night and one of my best memories was sitting on the veranda watching the lights slide by. Beautiful!