Does anybody believe that certain board designs actually release from the water with less tension on the knees?
These boards with tip channels and the like would be assumed to release more smoothly or is it all about technique and timing?
Release out of the water is not what screws the knees. Its hard landings, crashes and smashing through chop on a stiff and unrelenting board design.
Board designs with more rocker and flexible tips can significantly smooth the ride and reduce stress on the knees. The down side to more rocker and to some degree tip flex is that are more powerhungry that a stiff low rocker board.
Narrower stance help your knees immensely. Hard to find twin tips with narrow stance these days though