How to develop foot upswing?

What training methods should I use to develop the upswing of my foot? Im talking about after footstrike, when the foot strikes back and is supposed to upswing over the knee and as close under the body as possible or somthing like that. Mine is very poor, my feet dont come up that high, resulting in a low knee lift aswell. Please help, this is one of the first technical things I will be working on first as soon as im all healed.

P.S. I can do very quick knee lift drills in training but my butt kicks are always slow/poor no matter how hard i try.

You may have a problem with quad flexibility. Try work on that before you make any changes to your technique.

Alrighty then, thanxs, probably that because It feel my foot can move much faster on my upswing (and buttkick drills), but something was blocking its potential.