I stopped doing anything but bodyweight leg workouts and couldn't be happier. When squatting anything over 310 made my knees hurt for days(smith or BB). I have had a number of knee surgeries and 2 reconstructions. I do have arthritis in both knees.
I have always had decent legs, from years of wrestling and martial arts. I started doing mostly body weight work, and a lot of bag work, and Thai pad work. My legs are as big as they ever been, my knees don't hurt and my flexibility has gotten better as well. After 4 months of not doing squats, I did a few reps with friends while at their gym and was able to rep 400lbs 8 times without any trouble. My prior max was 450lbs for 5 reps. So I don't think I have lost an ounce of strength. I still do stiff legged Dead Lifts with weight but that is about it at this point.
Different training for different people...