RSD definately spreads. It started in my left hand & arm up to my elbow. I went into kind of a remission stage for 2 years. We had know idea I had RSD. Now within 7 years I have RSD in both hands up to the elbow and the right hand is spreading up to the shoulder. It has become increasingly worse over this last year and I wait to see where it creeps next.

Having relatively mild (still able to work) RSD in left leg for over twenty years, I never thought it would spread, either. Last year, my right leg starting getting symptoms and recently the arms and hands, too. After all this time, it is unlikely that over-compensating is the cause.