Replying to How to Prevent a Sprained Ankle?

Okay so I was skiing yesterday at my hill's first rail jam and I was going for a 270 out and I only got about 180 out and I kinda washed out but my binding didn't really release and my ankle/knee got kind of twisted and now I have a twisted ankle. So I was just wondering what could of caused this? I mean I never even knew it was possible to sprain an ankle with a ski boot on.

So

Should I get new boots?
Lower my din?(It is at a 7 or 8..I forget)
or was it just cause I failed at 270ing off and washed out and had some bad luck?
Oh and I have marker free 12.0 bindings and technica sx9 boots(or something similar to that)

Any help would be greatly appreciated since this sprained ankle is extremely gay and I really don't want to get another one and want try to prevent another one.