Cycling is great, I have a biggish chest and... it gets sore enough for a week every month that I don't want to jump around. Never have any problems with cycling unless the roads are really bad. XD As for your knee, you could even go to a bike shop and make sure your real bike is properly fitted to avoid hurting the knee further. If you don't have a bike and are in the market for one, look around for recumbent bikes as well as traditional upright bikes.
With my depression sometimes biking is the only thing that I have the attention span or motivation to do, in terms of exercise.
The other thing I found is low impact is Just Dance.
I'm not sure which consoles it's available on. I have it on the Wii. The thing is, it only uses one controller, so you technically don't have to do all the dance moves with your legs or even your other arm. So you can control how much jumping and squatting you actually do, while doing all the swaying and arm-waving you want.