Besides "go see a sports medicine specialist". Can anyone give any insight to the following;
When I go to get out of the saddle and climb standing, I have a *really* sharp pain in the back of my knee cap. If I slightly adjust the postion so that the whole leg is a little straighter the pain doesnt occur. It's an pain/no-pain situation rather than a more/less situation. It also seems to occur more often on one bike more than another.
Arnie Baker, the cycling doctor for Bicycle Mag, lays a lot of the blame for knee problems on pedals with too much float in them, or incorrect float adjustment.
When you adjust your leg to be straighter and avoid the pain, could you actually be twisting the foot into a better position for you? Are both your bike's pedals adjusted the same or could they be slightly different? One fitting you better than the other?