If you can find access to a stationary rowing machine that would probably work.
Edit: Crunk beat me to it lol.
Edit 2: If you can still use your legs I would imagine any rowing machine would work. I don't feel any strain on my legs when I do it but it may be different if I had surgery so I cannot speak to that, however you could try it lightly.
Last edited by EyelessCrow; 2013-01-14 at 08:52 PM.
I have a zero arch also. I haven't had to have surgery but I do have to avoid running.
What I do is walk as fast as i can on a treadmill but I do it at a really good incline. This gives your body the same workout heart-rate wise as a decent jog.
Not sure if you are limited to the point where you can't even do this, but If not, I'd highly suggest it.
A lot of gymns have indoor or outdoor (heated) pools. So, ya swimming is good.
I'm a bit confused though, if you have bad knees, and can't run... can't you just do an Elliptical machine? From my understanding, running is bad on your knees because of the shock of impact with your foot hitting the ground. Both biking and elliptical should be ok in your case... that is unless you JUST HAD the surgery.