In reply to Sharp:
Definitely worth haveing a session with a senior/experienced physio as (given your description of the location of the pain deep behind and when externally rotated) it could be a labral tear of the cartridge. It turns out I have been living and climbing with one for years and keep re-injuing it, gradually making it bigger, takeing longer to recover from flair ups with serious consequences if it fully rips off the bone. A senior physio suspected this after examination and MRI confirmed. I am now awaiting surgery.
Had I know earlier that it wasnt 'just a muscle pull' then I would have gone down the surgery route earlier before I weakened it further, and lost more time to re-injury.
My GP (when I eventually went to see them) made the referal to Senior Physio, who referred to MRI, which lead to Consultant orthopedic appointment.
Hope it's not that bad for you, but something to bear in mind if treatment for muscle pulls does not fix it, or it happens again in same place. Definitely worth seeing someone.
Post edited at 01:03