The crappy thing about Pred is it totally counterproductive to what we do. It causes water weight gain, it increases hunger, and catabolizes lean tissue.
But, take the time now and use it as a starting point. The scale is a terrible thing because water weight fluctuates so much throughout the day and even moreso in women. You are going to be fine. BTW, how is the knee going and have you gotten any more information on it?