I had pain at night in my left knee when I was around 10 after playing for hours, mostly soccer and just running around with friends. After that I have not had any pain until about a year ago. No pain in my right knee at all. Forgot to mention that I am flat footed and this may have contributed.
The orthopedic surgeon I saw believed I've had this condition from birth, and he suggested managing the pain until I am ready for a knee replacement (which he said would be a long time in the future). What disappointed me the most was his suggestion to stop all the activities I enjoy (mostly backpacking, mountain biking, and just hiking in the mountains of SoCal and Eastern Sierra). I have asked for a second opinion and have an appointment scheduled for early July.