I just wanted to say that I can understand your concern because my friend (read my post to Karen above who is stage 4 also had arthritis with pain in the back and hips before she was diagnosed for the second time. She said she had just assumed the pain was due to the arthritis, but that in looking back on it, she now realizes that pain was a different kind of pain. I don't know exactly how it was different, but I guess my thought is that if you feel persistent pain that is different in any way from your "usual" arthritic pain, see your onc. and ask if you can have a PET scan. The way my friend came to be re-diagnosed was on her annual visit at which time her onc did the CA 27.29 blood test. Her number previously was in the 40's, but on that visit, it was 700+. At that point, they both knew something was up, so her onc ordered a PET scan, which is how they discovered the metastasis. I had one other thought about this. But again, don't be afraid to ask your onc. A year or so ago, I told my onc that I have pain every day (which is true), so how would I know if it's "normal" pain (since my arthritis pain increased significantly after treatment and 5 more knee surgeries). He had no problem ordering the PET scan, and it turned out fine, but it was nice to have that assurance. Also, I could move on because knowing it wasn't a recurrence allowed me to explore ways to deal with the increased arthritic pain (PT, exercise, etc.). Hope that helps.
Hugs & prayers,