Hi, I'm going to have THR in two weeks and wish they could do a little tummy tuck at the same time! I'm not heavy, but would like to be flatter in front. When my hip gave me problems my activity level went down and weight loss became difficult. I am really concerned now that I found out I am not supposed to ever lift my knee above a 90 degree angle, how can I do crunches or otherwise exercise my middle???? Thanks for any suggestions.