Also if you sit too forward on the bike even if you are not clipped in you might put extra stress on the knees.
You can read up on it yourself, but the gist of it related to sitting position fit and knees is that the tip of your knee should be vertically right on top or behind the ball of your foot when you are pedaling. ( measure it on the front leg when the pedals are parallel to the ground )
The more forward your knee is than the position I described above the more stress you put on the knee. Just another thing to check.
Interesting. I haven't noticed any knee issues resulting from cycling but I'll definitely check it out.