All the above seems pretty interesting and worth pursuing. Just a few additional comments. I've had a chronic problem with my kneecap. No one has been able to accurately diagnose it. 'Patello-femoral syndrome' seemed closest. my massage therapist thinks it's the ITB. but, fortunately, it's not as painful as what you describe; it's just an annoyance that i have to be careful doesn't get any worse.

my experience is that the usual 'go to' medical professionals are not good at this stuff. the best results i have had were from alternatives to western medicine like trigger point therapy and massage therapy -- not paid by my insurer, alas. but physical therapy with a talented therapist might work. i've heard lots of good stories, just haven't witnessed it myself.