My knee hurts from sitting down and working long hours. what should i do?

Take breaks: You can take breaks and walk for 10-15 minutes during extended sitting hours. You can also exercise while you are sitting. Over the counter glucosamine / chondroitin sulfate 1200 mg is helpful if taken twice a day for many months.

Move frequently: Sitting makes your joints stiff. So every half hour get up and stretch and take a quick walk around your office or desk. Bend your knees under your desk frequently.