Moving your seat height the same as your saddle will maintain the position of the knee. If the saddle is moved 1cm forward, the saddle must go 1cm higher to maintain knee position.

Picture this exaggerated version where your knee starts at 90 degree angle while seated, pedal frozen in place. Imagine the saddle moved forward all the way to where the knee originally was, now raise the saddle straight upward the exact distance it traveled forward. The knee is now in its original location.

Edit: After drawing it out, I see that this will only work at 90 degree angles. The multiplier isn't a single number.