1 you do not mention testing of the SI stability. SI tends to give multi segmental lumbar problems. In which position is the SI?
2 This seems to be a multi segmental problem.
3 Any radiation?
4 Kissing spine? since Pt has a more or less flattened + extended lumbar spine.
5 Bilateral, e.g. kidney involvement?
6 checked on thoracic mobility?
7 quadratus lumborum: triggerpoints?
8 on palpation any triggerpoints found?
9 Family history of e.g. RA, ankylosing spondylitis?