As Vicki pointed out, I have both MS and RA. Maybe I need to talk about that more. :)
RA can involve any and all of the joint areas which you have mentioned. Mine started in my hands, but my first major attack which we didn't know was RA yet occurred in my left shoulder which swelled up to almost twice its size and was immobile for awhile. With my hands, the neurologist thought it was carpal tunnel syndrome and I was eventually referred to a hand surgeon (scary!!). The surgeon treated the inflammation with steroid injections and later referred me to a rheumatologist.
Bingo. I was diagnosed with RA on my first visit. I had brought copies of all my bloodtests dating back five years (I always ask for a copy to be sent to me at the time the blood is drawn), xrays of my hands and fingers, and a history of my symptoms and the treatments which had been tried.
Something I've learned in researching comorbidities for a series of articles on MyRACentral.com is that fibromyalgia can cause joint pain similar to arthritis. Also lupus causes wide-spread pain in some people. The thing which is in common with these diseases is that they are treated by a rheumatologist.
It is wonderful that you are thinking ahead for your visit to the neuro. Prepare a list of concerns, symptoms, and questions to discuss during your visit. Oh, and of course, try to see if he is any closer to diagnosing MS yet (or some other neurological disease).
If you've got other questions related to MS/RA, please don't hesitate to ask. I'm not really an expert but I can certainly share what I know.