Can Lipomas On Knees Damage The Soft Tissue Around The New Knee Replacement?

My mother had her second knee replacement 6 months ago. 10 years ago she had the first knee replaced. She has large lipomas on both knees, which where there before the second knee replacement. They are very large and are impeding her gait because they rub together. She was referred to a plastic sergon to have them removed. My concern is that these lipomas are right next to the knees and could damage the soft tissue around the new knee replacement. Any thoughts on weather she should wait for the tissue to completely heal would be greatly appciated. Also, do you have any other sugestions on reducing the size of the lipomas without surgery. She is 75 years old and could stand to lose about 35 pounds.