[BerntR]

I read somewhere that Tiger injuried his knee on a skate board as a 13 year or something. That may have a lot do do with his current knee problem.

Having said that, how he has charged his left knee post impact has never looked healthy to me.

Tiger had tip in one of the golf magazines a few years ago about "snapping his left knee" when he needed an extra few yards. That must be one of the worst golf swing advices ever given.

There may be good geometrical reasons for straightening the left knee 100 % at impact, but this is not a healthy solution physiologically. Something has to slow down the pivot rotation after impact. If the left knee is straight it will absorb a lot of the torque and injury will follow. Ideally the deceleration should be handled by muscles and not by bones and joints.