I am a fellow GenXer with the same types of knee issues. You are going to love your ebike when you get one. An ebike is like a safety net for me. I can go out and ride as hard as I want for a workout, and when the knee starts acting up I can up the assist level and take a break. Sometimes I can go back into “workout” mode other times It just helps me get home with no worries about any hill or mileage in front of me.
If you like maximum assist on the way home, you would love a throttle for those final few miles when you are spent and want a break, but don't want to stop.