Look up ITBS and see if your symptoms match. Even if it isn't, maybe sight-specific stretching will help? I've had chronic knee pain for years, and I've recently been going to a PT, after seeing the doc and having the x-rays. Bottom line - stretching has helped immeasurably, and I think might help regardless of the etiology.
An example specific stretch:
lie on flat on your back, pull your knee up to you chest then gently rotate the leg into the body. You should feel the stretch on the outside of the knee.

Sue