April, you can start to lose even if you can't exercise right now. I too have a hard time exercising because of bad knees. So I just started to watch how many calories I was eating and decided to eat around 1400 - 1600 a day and the weight starting coming off without exercising. I know it's important to exercise, but don't think that you can't lose weight without it. Once you see the scale go down, you can add some light exercise or start walking a little (hopefully the weather will cooperate by then). This worked for me and I have a very sluggish metabolism.
You can do this!