^^^^ good recommendations above.
i agree with lessening the weight on squats if they hurt your knees, you can hammer away at 135 on squats and do heavy reps of them and really get a burn going. then go heavy on deadlifts.. that will definately grow your legs.
i would also load up in joint help.. krill oil, omega cage free eggs, extra virgin olive oil (drink a spoonful before the gym), avocado.