Consider the ITB again, as I've mentioned way earlier somewhere.
I have known cases where patients go for all sorts of scans and tests for every conceivable pelvic and sacroiliac parts and came up short, and it turns out to be a way thickened and numbed ITB.
Once the ITB becomes overused, it can cause/contribute to anterior pelvic tilt, impede hip rotation, and mess up the timing of your affected leg leaving and touching down on the ground.(This, of course, messes up the coordination
between both legs while walking and running, leading to a myriad of hip and leg injuries, not to mention slower race times.....)
The worst part of this is that one usually does not feel any pain along the conventional areas (like the knee), but might feel it at the hamstrings, groin, adductors. All this while the ITB can feel numb.
Most doctors and therapists are trained to look out for symptoms that are taight to them from med school, and so may miss out on the ITB being one of the causes. And from my limited experiences, ITB is one of the victims of poor posture, form and core strength.
Once it gets bad, it perpetuates that pattern of bad posture/form because the rest of the body needs to compensate and adjust according to the shortened and way thickened band in order for the head to be upright and for the both feet to touch the ground. The quaratus lumborum of the affected side lengthens while the same side shoulder 'freezes' up. This allows the now functionally shortened affected leg to touch the ground. But the lower back at this stage has adopted the 'swayback' position, leaving the glutes unactivated. This overloads the quads and hip flexors, which become shorter, leading the an anterior pelvic tilt on the affected side.
If u feel u have truly exhausted all options, try foam rolling your ITB on your bad leg and see if there's any reaction. Try comparing the texture of the bands between both hips. See if this can lead u anywhere.....