Good for you, battlin' thru all that pain; sometimes, we have to push ourselves a tiny little bit. But, don't overdo it now: you don't want to hurt yourself in any way and end up out of commission for a week afterwards. I also like to do the hand weights, stretchie band, plus arm & leg toning exercises as well.
I heard a doctor on the net say that doing small spurts of walking: ie 5 or 10 minutes at a time, for up to several times a day is just as good as if you did it all at once. I'm sorry I don't recall his name to give him credit, but he has a good point -- exercise is exercise ... and I think it may even be better for us to spread it out over the day, so we are burning off what we eat over the day too. It kinda makes good sense really.
Keep it up; and glad you found your way to our thread (Physical Challenges) and you noticed the other thread about Prednisone and weightloss; lots of folks around here know what you are going through and can offer you support ...
Prednisone Face
As I said in an earlier post, I'm going to start by counting carbs(diabetes) and sugar intake. And, of course keep up the walking. BTW- I have also done some legs stretches and arm curls with a 5lb weight in ea hand!! 
