HI
for those who didn't know about it...my research was in the form of a survey of 101 dojo, purely gathering info, a snapshot if you will. The link follows...the 2 most interesting things to me were that a small handful of dojos were responsible for a large proportion of the acute knee injuries and that despite many complaints - including MINE - over the yrs about feet sticking to soft mats, there didn't seem to be a correlation btwn wrestling type mats and acute knee injuries.
http://www.zanshinart.com/Aikido/AikiKnee.html