On the one hand, I want to exercise more for general health reasons. I don't want to end up old and find out that immobility has snuck up on me, nor do I want to discover that it's really true that being inactive increases your risk of dementia. (It's all well and good for me to assert that dementia doesn't run in my family, but that only works if I ignore my father's mother. Which I mostly do, but still. Probably I should stop doing that.)
On the other hand, I don't want to exacerbate existing joint issues, which would really suck and probably not help my old age mobility at all, especially not if that's connected to arthritis. In the past month my mother has mentioned off-hand an alarming number of relatives who were severely restricted due to arthritis at rather young ages - and that's only counting the ones who developed it in adulthood! There's at least one cousin of hers or her mother's who was apparently "totally crippled" before puberty. She can preen all she likes about how that gene seems to have skipped her, I see my sister increasingly worried and yet dodging the thought that she might already be developing arthritis. She's not even 40 yet! (She ought to go to a doctor. I think we all know that neither funds nor time is really the reason she hasn't.)
So clearly the thing to do is find some 15 or 20 minute daily exercise routine that's reasonably high intensity but isn't going to screw up my joints, at least, not more than they already are. Preferably something that can be done by somebody with no real coordination - I can't jump rope, I can't ride bikes, every day I nearly trip over my own two feet/my pants/the dogs and break my glasses.
Maybe I should just buy myself an exercise bike. When I don't need to balance, I am very unlikely to fall down. I'm not worried about myself so much as my poor glasses.