Hi Lula and welcome to HW!
There is a lot of crossover between IBD (inflammatory bowel disease) and RA. Crohn's Disease itself can cause joint pain, but you'll find a lot of people on the board who do have both diseases. I'm kind of the opposite of you, having first been diagnosed with Crohn's and am now being treated for RA. Luckily, the treatments are often very similar so you can treat both diseases with the same set of meds.
As for your concerns about blood, what exactly do you mean by "large quantities"? Also, is this bleeding only since the colonoscopy? If that is the case and you are still passing blood several days after the colonoscopy then you need to call your doctor's office stat and let them know what's going on. That said, if you are seeing blood in the toilet bowl, be aware that a little bit of blood can look like a whole lot in the water. A lot of people with Crohn's and UC pass blood with every or nearly every BM. I know it can be awfully scary at first, but a little blood should not be something to get too scared about. If you are concerned though, just call the doctor's office. That's what they're there for. The doctor is probably waiting to start treating you until he gets the biopsy results back because they'll give him a better idea of what he's dealing with and that way you're not possibly receiving an unnecessary treatment.
Hang in there and keep us updated on your results.
29f, PhD student, originally diagnosed with Crohn's in 2/06
10/09: Prometheus test shows results consistent with UC
10/12/09: beginning treatment for arthritis
Currently taking: 7.5mg methotrexate weekly (pills), 2g Pentasa, tapering from 20mg prednisone, 150mg Trazadone, multivitamin, vitamin D, magnesium, probiotics, folic acid