The PT will do some particular tests that can give them a better idea where the issue is. He'll be able to give me some stretches targeted to the issue and that will give us more information when i see the OS. as i understand it, if it seems to be related to the psoas, they'll scrutinize my next xrays more closely. They can also see an issue sometimes with ultrasound or do an injection in the psoas to see if the pain goes away. An MRI can also be used to see if there's an issue. If (big if - could be nothing) there's a problem, treatment depends on what's causing it but could include surgical lengthening or release of psoas.
Hopefully, I'll know more this afternoon. in the meantime, I'm not in agony and still better in most respects than I was 3 months ago. If I had to give up going up stairs, it wouldn't be the end of the world (and would be a good excuse to never let my trainer get me anywhere close to a stairmaster!), but I'd really like to be able to put on socks without gymnastics and pain!