Bry, for me they go by the symptoms I present. Can usually tell thing's are going a bit haywire by the increase in BM's, bleeding or not, and much like you, the aching joints. I'm quite lucky in that my Gastro says that I know my body far better than him, and then we agree on a treatment plan. I've had a flexi sig as well just to progress check the healing- quick and painless, and can see exactly what's going on.
Hope you're feeling better soon
Andrea