rider stance

I talked to my doc about this after he cleared me to ride and he said to keep my stance and everything the same. I was told that if its something im comfortable with then roll with it, and not get use to a different stance width or duck. the only thing i can see from my non medical background is being to much ducked and under rotating a spin and trying to slide the rest of it around on the water having an effect on your body mainly knee/knees. which just so happened to be my case altho i don't consider my stance very ducked