What do you suggest if my knee hurts when its in the same position for more than half an hour?

Try keeping leg out.: Try keeping your leg out straight if feasible. Your symptoms are suggestive of patellofemoral ( kneecap) pain which can be exacerbated by keeping your knee flexed(bent)as the patella( kneecap) gets tucked into the 'groove'( trochlea) of the femur bone.If your symptoms don't improve w/ this and simple hamstring stretching / NSAIDs see an orthopedic surgeon. Good Luck!