Originally Posted by
aschick 
First: ACL injuries are common in a number of sports where you don't have a huge lever attached to your foot. The leg injury unique to skiing - and the one that modern bindings are designed to reduce are lower leg fractues. Good point, however from what I understand, slow mo's of basketball injuries ususually show the player has his/her hips behind CM, often lands on one leg, and often has an awkward landing involving a turning motion. So it may be more like skiing than it seems.
Second: We why not focus more injury reduction strategies at the site of injury. There are knee supports that can provide some additonal protection to the ACL. If you are concerned about such injuries then wear one. Again, from what I understand and what orthopedists have told me, braces help stabilize an already "loose" or previously injured knee, appear to significantly reduce re-injury. But they do not apparently fit closely enough or "react" quickly enough - it might take a full cast, literally, which could, ah detract from skiing movements - to prevent the initial tear. As you mention below, ACL does not necessarily involve a prolonged movement, more like a microsecond of overload on an already taut/stressed ligament.
Third: If developing a binding along the lines of a knee binding was the answer, and it was mostly an engineering problem, then what was stopping major companies from developing a similar design? Apathy? Economics and psychology, I'd assume. This is not a national crisis akin to terrorism or bank failures, where we might call for concerted federal/private action. Statistically, most skiers do not ever blow out their ACL's; ACL is not even the most common skiing knee injury, just the most serious. So most skiers do not anticipate they will have a ACL rupture ("won't happen to me, I'm careful,") and therefore most skiers would not pay as much for a binding as for a ski to prevent something they do not fear.
Fourth: from personal expereince when I have tweeked my knee skiing, I have to agree with SJ's assement that in that very vulnerable position where your hips drop below your knees, it takes a very small force to pull or tear the ACL. Significantly less than would trigger a release. If you are looking for a technology to reduce that kind of injury it would need to be integrated into the boot itself closer to where those forces occur. Yep. Or a mechanism - I've seen something like this pictured on one of the knee sites - that runs from knee to ski, which would make us look like Ironman (and maybe ski like him).
OTOH, getting back to my intermediate comment earlier in this thread, it seems to me that ALL skiers CAN get into a position that threatens the ACL, but experts are less likely because they spend less time in the backseat, jump better, and are more experienced about falling.
On one of the knee sites there's a great/sickening video of an intermediate female doing a little mini-jump (looks to be in chalky ridgeline terrain beyond her ability), sitting /falling backwards onto her skis (thus loading and locking her ACL), struggling to get up again while still moving foward across the fall line (thus putting more stress on it), and all of a sudden her downhill ski deviates suddenly (looks like it gets pushed by some light chop), and she cries out, starts sliding downhill in a heap. (Her doofus male companion is taking it all very light-heartedly, laughing while he asks if she's all right. She is not.)
IMO her skill set, or lack of it, plus someone's bad judgement, caused that blow out, not her lousy binding. My .02
