So currently her left shoulder AND right shoulder AND left ankle are all in excruciating pain? Or do they just alternate? When did the pain onset? Has her ankle only just started hurting?
I'd be tempted to risk the lymphoma and get one last x-ray, then after that, combined with previous records, you have some pretty strong evidence to say she is faking it. Dubious: Maybe 'accidentally brush her arm to judge her reaction? Probably would not do this!
The time is interesting - do addicts/munchausens typically pop along at 5am when most people would rather be sleeping? Maybe they do.
I also find it interesting that they are going to a private surgeon. Obviously could be coincidence, but is it because the NHS have refused to treat her in the past? Would this not be in her history?
It could be some other source of pain, maybe neurogenic, but the pain localizes to her shoulders, then when they are examined it localizes somewhere else... i don't think this is any other problem that requires investigation.
I would take this up with her and her parents. Explain the situation - there is no evidence that she has ever had a dislocation despite numerous x-rays including 4 (i'm presuming) negative tests in the last couple of hours despite complaining of extreme pain only moments before. Whenever one area is examined the pain suddenly changes to somewhere else. She has maxed out on morphine etc and there is nothing else you can do for her if all of these dislocations miraculously heal themselves every time they are examined. Go home and see what the orthapedic surgeon says - this will provide a conclusive view as to your problems. For now, there is nothing we can do.
If i get shouted at or threatened with GMC hearings then so be it.
I presume this is ok having been given morphine etc - you said her O2 sats were ok.
EDIT yeah sorry 'faking it'is wrong - i just didn't want to type munchhausen lots of times!