Ultherapy may be an option for you, however, that depends on what you mean by weight loss(how many pounds), your age(younger versus older and pre versus post menopausal) and what you mean by sagging legs. Ulthera is excellent at tightening certain body regions(more than others) but certainly within limits. I say this based on five years of experience. Since words like weight loss and saggy mean different things to different people I am not sure if Ultherapy will help you. Ultherapy can lift buttocks, thighs and knees reliably, but what you may require can only be answered with additional information.
Simply put Ulthera may not be your best choice. For several reasons. First, Ulthera is designed for face, neck and the thin skin of the chest. There is very little evidence that it works for the really different skin quality of the thighs. Second is the cost. It would be staggering for a treatment that is totally off label and un- proven on how it works on the thighs. So instead see my article about ThermiSmooth Body which just got FDA clearance this past winter. We can treat the full thigh but I have a hunch you might well need 2 series of 6 treatments each. You’ll need patience because your best results may be 6 to 10 months as your body rebuild the collagen
Please post photos for further evaluation. If there is excess sagging skin, you likely will need surgical removal. Wrinkling of the skin can be improved with skin tightening procedures and lasers/microneedling. We often use thermiRF with thermage and sculptra for improvement on the body quite frequently. Best, Dr. Emer
Ulthera will not tighten or lift excess, lax skin of legs. Depending on the extent of skin excess and loss of elasticity, you may need surgical excision of excess or damaged skin but since you have not shared any information or pictures, its not possible to provide a relevant response.