WIll J-Plasma on the front of my thighs rid them of that cottage-cheese look and slight sag around the knees?

Thank you for your question about Renuvion.
Renuvion (also called J-Plasma) is the newest and most powerful minimally invasive skin tightening treatment device that utilizes helium and RF (radiofrequency) to create a targeted beam of plasma for subdermal skin tightening.
It can be used to treat any area where skin tightening is desired, but is commonly used for face, neck, arms, breasts, abdomen, waist and flanks, inner thighs and legs. This skin tightening procedure is commonly combined with liposuction to produce dramatic long-lasting results. Recovery is similar to liposuction with 1-3 days of downtime, and bruising/swelling resolving over several weeks. Results are seen immediately with tightening continuing over the next 6-12 months.
The results in your case may vary, Renuvion is good for tightening skin, but is not able to get rid of cellulite. If that "cottage-cheese" look that you are referring to is due to cellulite, I would not expect much improvement. Renuvion is good though for tightening skin around the knees and when combined with liposuction can make the legs/knees look thinner as well.
Hope this helps!

The answer depends on your physical examination, specifically how much skin laxity and descent you have. These techniques are better at tightening than they are at lifting. Some patients have too much descent for non invasive procedures and require an excellent cosmetic alternative, a lower body lift. When done expertly it is an excellent and well tolerated alternative. Also some patients may benefit from synergistic skin tightening procedures to "layer" contraction, and thereby augment the tightening effect. 

Cottage cheese appearance is mainly due to cellulite and fibrous connective tissue bands connecting skin to muscle to form cellulite and j plasma is not the ideal treatment goal of cellulite . J plasma may improve the area but the main effects are to tighten loose saggy skin . J Platzy refers to j plasma treatment of the neck combined with a suspension sutures to help lift the neck . This is j plasma done with the suture under the skin to the neck only , where as j plasma elsewhere on the body is currently known as j plasma soon to be known as renuvion