The FDA has not approved coolsculpting for the knees. Consult with a board certified physician who can provide surgical options and coolsculpting to determine the best treatment plan for you.
Currently, the handpieces available for CoolSculpting are too large for the knees of most people. It is important for the handpiece to fit very securely on the area to be treated in order to achieve desired results. However, Zeltiq, the company that makes CoolSculpting is developing smaller handpieces that will offer more options. Look for a physician you trust and respect performing CoolSculpting in your area. They will keep you informed about new developments with CoolSculpting including new, smaller handpieces.