My hubbies RSD in his leg did not spread. He actually went into a remission of sort (after about 5-6 years of living hell) with having just a few skin sore break out here, and there, having to always walk with a brace and on and off days of managable pain & cramping. I contribute this to the fantastic physical therapy team he had, Dr's who recognized the signs early on, a pain management clinic and a lot of hard work.

He does have RSD now in his arm caused by surgery to the ulnar nerve. Sometimes he says his shoulder aches as well but sometimes I also believe this could be caused by the way he carries himself - in a protective mode with his arms.

I guess it's the individual, the dr who diagnoses, the type of therapy that works well for them, and a lot of other factors. If all the right things are not found as far as treatment goes along with early diagnosis I would imagine spreading is a lot more common.