Can injectable fillers be used for sagging knees? (photos)

The short answer to your question is "Yes!"  Injectable hyaluronic acid-based skin boosters have been used successfully for treating sagging elbows, saggy knees, and even saggy upper arms. Skin boosters work by promoting new collagen and elastic fiber synthesis to improve the quality and smoothness of the skin by enhancing hydration and promoting greater elasticity. In the U.S., we do not as yet have specific skin booster injectables available. For this reason in my NY office, I typically use Restylane Silk for this purpose. In my Israel satellite facility, where a far greater number of dedicated skin booster products are available, I typically use Viscoderm Hydroboosters, Profhilo, Juvederm Volite and Restylane Skinboosters. As to how much it costs, that will depend upon the experience and location of your physician and the particular material or combination of materials and amounts needed to get the job done. Be sure to consult with an experienced board certified aesthetic physician, since this location is not for novice injectors accustomed to injecting simple Juvederm or plain Restylane into smile lines. Best of luck. 

Flexibility at the joints naturally requires some looseness/wrinkling of the skin, so a bit of saginess is normal and necessary.  If it is excessive but not enough to require a surgical intervention there are some in-office treatments that are available.  We have had success with “hyperdilute” radiesse.  Radiesse is a calcium based facial filler that we mix with saline and lidocaine (for numbing).  Mixing it like this really thins it out and makes it suitable to inject in the skin or right under the skin to build collagen and tighten things up.  It works well on abdomens and recently I just treated my first patients on their knees and elbows.  So far so good.  Combining this treatment with laser, microneedling and/or PRP may yield even better results.
Depending on the surface area to be covered, treatments generally run between $1,000 to 2,500.  The more treatments the better—I recommend starting with 3 treatments 8 to 12 weeks apart.
Hope this is useful info for you.  Best,
Dr. Amy