I would second going to an Orthopedic Surgeon to get checked out. I went to one that was highly recommended. Unfortunately for me, after x-rays and an MRI, he told me that there was nothing wrong that was operable or that could be corrected with the orthodics. He understood the stress I was going to put on my knees and recommended experimenting with over the counter knee braces to try to find something that worked. I did feel a lot better after I saw him that I didn't ignore a potential problem that might have prevented me from completing my trip.

If you are having knee problems, there might be something an orthopedic surgeon could do for you that might correct a long term problem before it gets worse.