Injured...

Looking for some suggestions on exercises that can be modified for a sore knee. I have been doing a lot of walking and elliptical since I started MFP, but the other day I took a wrong step on a stair and tweaked my knee. Doing my usual 5k is out of the question as I don't want to make it worse, but I want to remain as active as I can.

This morning I did some recumbent biking (it held up ok), but looking for more ideas to get me through the next little bit. (Cardio related...I can do some strength for upper body and core, just have to hold off on lower body for now.)