I doubt if dropping from 25# down to, oh, say 17~18# in bike weight is going to fix your knee. I'd suggest a professional bike fitting including cleat & pedal fine tuning.
If you're down to dropping weight from the bike, I'm assuming your gear is at a minimum. You might consider short touring on an endurance road bike like the Specialized Roubaix or Giant Defy Advanced 2 (both with 1:1 low ratio from the factory), using bikepacking gear.