How to injure knees?

Having read Koma's excellent question thread about knee injury prevention, I've got a question for you guys:

For those of you that have had knee injury, how did it happen? Don't most of these injuries happen in competition or in environments in which the tempo is "cranked up" a bit, OR when doing stand up training/grappling? I'm wondering if I should feel relatively safe from big injuries like these if I stick to friendly rolling. Or can these injuries happen anytime, even if you're just grappling in a relaxed manner?

FYI, I had an ACL injury myself in Judo, when doing stand up "randori" (fell badly off my opponent's uchimata (inner thigh throw)). When I was almost healed I decided to try out BJJ, as I heard that ground grappling was easier on the knees and the body in general. Maybe it was fate, because I'm quite happy with BJJ. But I'll probably check out Judo again sometime. It was a lot of fun, too.

So what do you think?

Has anyone been ok going back to training after meniscus or ACL
surgery?

I had both ACL and meniscus surgeries. No problems training. Did get patellar tendonitis really bad a while ago, but took some anti inflammatories, plus ice and compressiong and i'm good to go. BTW I did go through 3 months of rehabilitation for the ACL.

Dogg

I was in a karate tourney in 85 and my oppponent used an illegal leg sweep to injure my knee...

those Cobra Kai bastards...

You're the best around!

In my first match in a tourney in November, I got taken down and I started to go into butterfly guard when I heard a crack in my left knee. Didn't bother me at the time, and I fought another match later in the day, but when I finished the 3 hr. drive back to where I was staying later, I couldn't walk. Took a couple days to get that back, now its a few weeks and I think I've hurt it again.

Damn lack of adamatium joints...

I did my ACL (initially torn, later snapped then reconstructed) doing Judo back in about '97 - not surprising after over a decade of abuse. Never could get the stability back into the join and as a result found Judo increasingly difficult... it changed my game so much that I found Judo just frustrating rather than interesting.

Since '99 I've been doing BJJ. It hasn't been a walk in the park knee-wise, but doing any full contact sport is going to take its toll. One rule I have is no lower leg submissions: I don't train them nor allow others to apply them - I NEVER want to have to go through major knee surgery again. These days I just manage the bad knee i.e. anti-inflams + rest + ice etc as required rather than fighting through it.