Try knee exercises,knee brace form drug store,,glucosamine pills,Advil (it works for the ups guy. )when these fail go to an orthopedic doctor.if lucky he can scope it and just suck out some junk from under the knee cap.many of my friends had tiny pieces of their knee floating under the knee cap causing pain.another friend had a silicone injection into his knee for quick relief.But this is not a permanent fix.
My knee acts up more in the cold weather.All winter I'm in pain ,summer comes and it's gone.