My knees are definitely a weak spot for me. Especially my left knee for some reason. Basically, I've found that I can still do squats, hammer leg curls, leg extensions, leg presses, etc, BUT I have to listen to my body and if it starts to hurt in an unnatural way, I take the weight down or move to another exercise.
I've found that if I maintain proper form, even in squats, I can push some serious iron. The machine squats hurt my knees, so I don't use the machine. But good old fashioned barbell with plates on either side doesn't - when I perform the movement correctly. Really, anything with free weights, done correctly doesn't hurt - okay, doesn't hurt in a bad way, it all HURTS.
Funny thing, I do have a treadmill desk, but it's in the basement and my treadmill is upstairs... probably should put to two in the same room.
Today, taking some of the advice above, I made sure to do compound exercises to exhaustion.
My workout today (in order):
20 mins on the treadmill.
2 sets of 10 - incline bench at 95#, then 6 reps at 95#
2 sets of 10 - incline at 65#, then 8 reps at 65#
2 sets of 10 - close grip lat pulls at 90#, then 7 reps at 80#
6 reps squat at 225# - I should have just dropped the weight and done more. My form was fine, but since I don't have the stabilizer muscles built up I was too wobbly to be safe. Next time I'll do sets at 175#
3 sets of 10 upright rows 40# (why does that seem so light?) - the last two of set 3 were barely countable, but I got them most of the way
I did the upright rows last today. The other day I did them first at a higher weight and it kind of wrecked the rest of my workout because my muscles were so fatigued after the rows. oops.
Hey, it may not be the power workout that some of you are doing, but it got my heart pumping and my muscles burning. So it felt great!
I actually look forward to the gym. My wife and I go together and motivate each other. Honestly, if it weren't for her doing upright rows across from me, I wouldn't have finished that last set. We were both wrecked, but I could see it in here eyes that she wasn't quitting on the last two, so neither was I.