Something to watch out for.
http://www.caringbridge.org/mn/curtmiller/history.htm
His was prostate spread to the bone, so actually any cancer (spread to the
bone) can cause back pain.
In addition, I've seen/read ovarian cancer present with back pain, liver
or pancreatic cancer present with back pain.

(and no, not all of you with back pain will be caused by cancer, but it
happens...)
So I imagine if back pain doesn't start to improve with the usual methods
of heat/cold, masssage, physiotherapy, it's fair to discuss getting at
least one scan and possibly some bloodwork (yet not overdo on the scanning
tests, because those also have risks, over a lifetime)