Q:

What are good non-bicycling exercises with a knee injury?

I banged up my knee in an accident and I won't be able to bicycle for a few months.  I'd like to keep up my cardio and calorie burning as much as possible during my time off.  What kinds of things can I do at the gym or home to try to replicate what biking gives me?  I will of course need things to do that don't involve my knee too much.
I can swim, but don't have access to a pool now. I can use my knee a bit. I have even gone biking. But, even a small ride (about twenty miles) will result in knee pain and weakness for days, up to a week.

A:

Swimming won't give you a 1:1 to biking (obviously) but it works out your whole body implicitly and is a great overall cardio workout and a great place to get started.
Otherwise I would take a look at spinning, low resistance.

A:

(Since I know nothing about the knee injury, I am considering your lower body out of the picture for working out.)
Take this as an opportunity to work the hell out of your upper body. Do pull-ups, chin-ups, push-ups, Hindu push-ups, bench presses, overhead presses, handstands, handstand push-ups, dips. Buy or make a sandbag and practice throwing and heaving it around. 
If you specifically want "cardio", try making a circuit routine out of a few of these (for instance, alternating between a pushing and pulling exercises) and do a set number of rounds or a set amount of time.

