First you need to find out why you are having the pain. As you mention, you are overweight and the pain could be due to many factors both related to and unrelated to being overweight.
Any type of liposuctioning will not get rid of pain and has a risk of making the pain worse.
Get a diagnosis and treat the problem.
I am aware of no evidence that SmartLipo will help foot and knee pain. If, as you say, you are overweight, you will benefit most by losing weight. Visit with your primary care physician and explain your goals. Your doctor can also make sure you are not having foot pain for other reasons, like diabetes. Best of luck.