Thanks for the kind welcome backs, Pflower and LL. I can only come back when I'm feeling stronger.

I would automatically got to the types of exercise that do not put pressure on joints: as in, swimming, light stationary cycling, and light, but repetitive weight lifting (take it very easy). Swimming is awesome because it can burn so many calories (and build up/ maintain so much muscle mass) without harming. Those are the first three I can think of.

There might be more suggestions online.