A 13 girl died this weekend after skiing into a tree at Alpine Meadows near Lake Tahoe. I’m a very keen skier and snowboarder and, although I wasn’t close to dying, I tore 3 ligaments in my knee after snowbaording into a tree last year. So I have a deep personal interest in the subject and have been evaluating knee guards as I get back onto the slopes.  What surprised me is that the girl was wearing a helmet. You’ll find that many skiers are wearing them these days, but apparently they don’t help in every case.