In reply to sbc_10:
Supination is merely a description of the position of the foot.
The cause will need to be identified to permit a solution.
Ask your physio or try a podiatrist for an assessment.
There's plenty of basic education & advice on the internet.
Until you've had a proper assessment, all you can do is avoid overloading it.
In essence, you're looking at footwear that constrains the tendency to roll onto the outside of your foot. Go for boots with good lateral stability- i.e. supportive at ankles, with soles that don't easily twist when you try and 'wring them out'
Although grossly oversimplified, think of the problem as the tendons either side of you ankle being like the reins controlling a horse- unless you have effective control of movement on both sides then the thing's going to veer off.