Continue talking with your doc about your leg/back issue. He/she is really in the best position to guide you through this issue as he/she is most familiar with your medical history and is able to do a full physical evaluation to held determine the best treatment plan for you.
Focusing your workout on a specific body part to shrink the fat in that area, AKA spot reduction, is not effective. The reason, fat distribution is, for the most part, determined by your genetics, but by following a healthy diet and exercise program, over time you will see results, but it is going to take time.
If you haven't visited our nutrition lifestyle resource center, this may be a good time to do so, as I believe education is the key to helping us break free from the diet mentality, therefore learning to live the healthy life we are meant to live. www.sparkpeople.com/resource/nutrition.asp
I hope this helps!