I have read with interest your ideas and I must admit the likelyhood of the problem being a regional pain syndrome and some psychogical and central problem (like to my opinion all injuries) But I was wondering if a muscular injury would have come up in the examinations as performed because as far as I can see it would not. One muscle could easily mimic internal knee problems (like the small oblique which pulls the fascia posterior in order to prevent pinching or another muscle which wouldn't liked to be extended) because it seems to me that in case of a muscle injury (or nerve pinching) the manipulation under anestaetics would have the same result: an increase in the range of movement. Her anxiety would not help to find out if it is a muscular problem because of her anxiety which would be less if she understood the problem. So it might be a good idea to tell her a story and stick to it. With sherrington techniques you could have a look if the range of movement would increase ( avoiding co contraction of antagonists).