I injured mine when I jumped a tall table top ( on a track ) at the same time the track owner decided to remove some loose dirt from the landing side with his loader. ( no flaggers or anyone in front of table, and there were still 3 of us on the track ).
Anyhow - came out pretty well considering - severed left ACL, Patellar, meniscus damage and a broken left femur condial. The right side was not to be left out tho, patella was in 3 pieces.
I also re-injured the left knee about 6 mos. ago when my body twisted over my left foot, which was well planted on the foot peg. A torn MCL, but that is all healed with no surgury. I wear an EVS on the left, and reg. shin guard/ knee cup on the right. In my particular case with the first accident, a knee brace would have done no good , but I think it minimized the MCL tear with the second incident. The first accident I was wearing knee/shin guards which might have spread a little of the impact? I do know the top side of the bucket sliced through them pretty easy, but I still think they helped and might have prevented a broken tib as well. My next piece of safety gear is a pair of asterisk or cells since my evs brace is getting a little trashed. You can never have too much of that stuff!! :)