In my (unfortunately extensive) experience of this issue, I've yet to come across a magic bullet - your problem is far more likely to be a bunch of inter-related issues, not something that can be fixed by a visit to a physio or osteopath.
That's definitely a good place to start of course, but I finally got things under control by obsessing about lighter basses and rigs, changing the way I play, visits to the osteopath, and (above all) doing Pilates for the last four years. The majority of my problems were related to my posture and to how I stand and hold myself (don't start with the ooo-er missus).
If you want a brief taster, follow the link in my sig to my YouTube channel and watch the presentation I did to two Bassbashes last year.
Good luck.