How do you tighten skin above knees?

Well, to tighten the skin above your knees you need to make the muscle supporting it more of a "bulge" to make the skin stretch over it. To do this you need to tone this muscle, so you need to work it.

An exercise that could do this is: stretch your leg out straight so that it wont stretch any further. you will feel the muscle stretching when you do this. Hold this for 5 seconds then release and repeat for 30 reps.

You should start to see results soon after starting the exercise!

Alternatively, if you cant be bothered you could allways go under the knife!