Hi Checkmate,
Congratulations on the weight loss...I know how hard it is to wage the battle of weight gain..Did you only reduce caloric intake or did you eat in a modified way as well?

Your question is one that puzzles me also. if I walk it hurts...a lot! If I don't walk, I will eventually lose even more muscle mass and even the use of my foot..
So where do you draw the line of too much pain?
If I walk to the point of a lot of pain, will this cause spread, OR will it retrain my brain into realizing that I can walk and therefore flip the pain signal switch to OFF !!

Youmight consider an excercise bike (if you don't already have one)...I get on the bike for 5 minute intervals sporadically when I can and try and get littles 'hits' of excercise that way..
Too much starts to cause the infamous 'burn' pain....
RSD is sooo unpredictable..
I hope you can continue to walk, even at a reduced level, as it is so good for the psyche as well !
Hope4thebest