Alright so 2 weeks ago i under went my last sugery (6 total) from a accident back in march that broke both my legs. Naturally being in a wheelchair for 7 months and having alot of my muscle cut away resulted in some pretty scrawny legs. I have a home gym (http://www.precor.com/cons/en/strs/325/ and it has some a leg press and other exercises to do. My knees still have pain in them so lifting alot of weight is pretty tuff and becomes impossible quik. I do squats with a medicine ball also. I have been working my legs out for about a month now and i still see hardly any difference at all in my muscle mass. What are some good exercises that i can do that dont require so much stress on my knees? I dont know if it matters but i am 24, 6', 165lbs. Thanks in advance for advice.