Hey Sas!
I've gotta put my vote in for cycling.
It's my absolute favorite sport cause it's hard work, tons of fun, and you get to see a lot of the city or countryside go by.
As far as your ankles, it will acutally strengthen them a lot. I had very weak ankles when I started and I could sprain them doing practically anything, but I haven't hurt them at all since I starting cycling.
The affect on your knees will depend on the type of injury you've had in the past. Cycling is good for some types of knee injuries and not good for other types. I'd say give it a try and see how your knees feel after a few miles.
Okay I've rambled on enough about cycling. I hope you have fun, whatever sport you choose!
~Anna
