Good Morning Ada,
Since I'm new to this RSD thing - I don't have any specific experience with hurting any (twisting, spraining) extremities.
What I do notice - is that when I get a cut, it takes a long time to heal and typically leaves a noticable scar. I had scraped my arm awhile ago - it has healed, but the area of where the scrape was is shiny. It's about 2" long - and is noticably shiny (and is in the area where I have active RSD). I had another scrape from a dish hitting my foot after it broke. It may have healed - but is obvious where it was (this is where I do not have RSD).
If I were to venture a guess - I would think that the RSD is involved. Is this on a finger that is on the same side/area where the RSD is? How long has it been? Just by what I've noticed with me, the skin, nerves are affected everywhere - it's all connected. Maybe not active in certain areas, but is susceptible. Would you agree?
I look forward to hearing what others think.
Beth.