Dragging knee during take-off

[surfing_peanut]

hey guys, just looking for any tips on improving my take-off.. I've been surfing a few years and have always dragged my knee when popping up. I can get by until it comes to larger steeper waves and then i become unbalanced..
I feel it's all in my head because i constantly practice my pop-up on land, but when i'm in the water i revert back to my old habit..

Its coming to a head now because i used to mainly longboard which is very easy to take-off on, being that your generally on the wave early. But now that i'm on a short board i have to be much more percise..

any tips? I already do a fair bit of pop-up practice on land..

any info would be mucho appreciated!!!!!!