I have the same pain and I haven't even got to ski yet, but it started after I got back into going to the gym. I've had it before (the sharp pain in the front of the knee when you apply weight, like the action of climbing stairs) and was told it's actually not the knee, but rather weak muscles in your quad that attatch to the knee. Therefore, one way to fix it is to try and straighten those muscles with excercises etc. Anyway, I'm hoping that's all it is because it hurts like a bitch. If in doubt though, go to the physio.