Basically here's the challenge: my knees are in rough shape, had surgery on the one, pressing movements are just killer such as squats and not so much but leg press. Recently I've been doing about 6 sets per leg of leg extensions (single legged) 12 reps holding at the peak at 15lbs (anything higher and it's killer), I feel next workout I'll possibly be moving up to 22.5lbs, in addition I do my calve routine. I don't do any hamstring work because that is part of my knee problem, they are overpowering my quads. I could try doing some light leg presses in addition to the leg extensions. Like what kinda rep scheme and set range should I be doing here since basically I'm limited to these 2 motions? Unless you can think of another one I'm missing. Thanks everyone.