Squat weight? Generally, I tend to find that when I'm not near a PR, my knees complain more than they otherwise do. Getting your lifts (sq & dl) comfortable in the low to mid 300s should help, too. If all that doesn't solve it, get a form check. Maybe you're "in your knees" too much. As for the knees forward during your squats, film it and see. Easy to spot, harder to fix.