I stay lean year round with only nutrition. If you see my pic, that is me year round. However, if I want to look "magazine" cut, I have to include cardio into my routine personally.
There are no magic exercises that are going to get you cut in the weight room, that will somehow, flatten your stomach. The fat on your belly is subcutaneous, which means it is directly under the skin. You can build abs until you are blue in the face, but that fat is still going to be located just under the skin and over the muscle.
Sorry, but that is the way it is!
If you really want to get lean and ripped, you have to make the decision to cut fat and you might sacrifice some muscle along the way. That is why you hear the terms "cutting" and "bulking." Many people will not worry about gaining muscle for a period with a primary concern of getting lean. Or, at other times, they might not concern themselves that much with bodyfat because they are concerned with adding muscle to their bodies currently.
If I were you, I would cut until you are at a level of leanness that you are happy with, and than build from there with a clean caloric surplus.
And by the way, find ways to work around a bad knee. Do low-impact exercises such as a bike or elliptical trainer.
Good luck.