Two months ago I knocked my left knee in a little accident. Recently I realized my knee hurts when I straighten my knee after bending for long. Help!

Kneecap injury. You may have injured the back of your kneecap (patella) when you bumped your knee. This may respond to rest, simple meds like advil, or aleve, (naproxen) and avoidance of prolonged bending or squatting. If not, see your doctor.