Sue,
It seems likely that the gut inflammation comes first and triggers a cascade of symptoms, since that's the way it works for reactive arthritis. Here is an animal study from 2010 that showed a mechanism for the inflammation spreading from the gut to the joints:
http://www.sciencedaily.com/releases/2010/06/100617120716.htm "One surprising finding was that bacteria in the gut could influence the development of an autoimmune disease affecting tissues distant from the gut. Diseases such as irritable bowel syndrome have been linked to gut-residing bacteria, but this study is unique in showing the mechanism by which a bacterium in the gut can influence the development of an autoimmune response that ends in inflammation and pain in the joints."
