First of all, welcome to Fitday and congrats on making the decision to get healthy and secondly, wow, 11 pounds in 2 weeks is amazing! You should not consider yourself "stuck" at all! Especially since you're in your "special" week. Lots of women actually gain water weight during that time and everyone is different so just hang tight until next week and like vsabino said, try not to weigh yourself too often. I know it's hard to resist. I have a hard time staying off the scale myself.
Is there a pool in your area where you could go swimming? That is really a great form of exercise when you have a knee injury. Also pilates or yoga might be good for you or any form of strength training because it builds muscle which will help you burn fat.