Swimming is easier on knees.

Runners/joggers switch to cycling if they've ruined their knees. This works if: a) you use your bike gears properly and learn to flip into easier gears so that you don't push on your knees overly hard, when the going gets tough b) your bike must fit you properly. c) positioning your foot properly on pedal. Using toestraps/toe cages or clipless pedals makes cycling even more like a dream...

Haven't gotten around to using weights yet. I know I lack upper body strength in my arms in particular. Which accounts for sloppy x-country skiing. Well, one day...

I do continue to marvel at women who really don't exercise (as much as I do) and are as slim or slimmer than myself at mid-life. It must the type of food and amounts.