Oooh, don't make me think about my knee. Right now, I wear a soft brace on the front. I should probably have it looked at (again), but I'm avoiding it. Two years back, last run of the year, bottom of the mountain, I hit a slush patch and my board just stopped. Instead of falling, I stupidly tried to keep my balance. My upper body lurched over the nose of my board, but my knee stayed in place.
It only hurt for a few days--then I was in a car accident months later that reaggravated it. It hasn't been the same since. Funny, the doctors couldn't figure out how I hurt my knee that way in the car accident. But since the accident insurance was paying out, I didn't fess up about the prior snowboarding incident. The webs we weave...
Moral of the story--take care of those knees!