It is probably safe, but I would first check with your orthopedic surgeon, especially if you intend to use it near you knees. Remember, however, results from RF fat reduction are extremely variable, and many times NOT impressive! I have had numerous patients come to me for traditional liposuction, after failing RF treatments, like Vanquish. Unless you desire a very small reduction of fat in a very well defined region, traditional liposuction is much more reliable. Also claims of "skin reduction or shrinkage" after RF treatment are anecdotal at best, and have never been confirmed by solid scientific research. Be sure to consult with a board certified plastic surgeon. Good luck!