It's hard to say genetics because we haven't really analyzed more than one generation of these types of injuries. Back in the day it was "a bad knee" or whatever. In research I'm doing for the Army (there are A LOT of torn ACLs, MCLs, LCLs, and PCLs running around a sandy rocky desert with combat boots on) we're finding the source is more poor biomechanics than anything. Certainly with re-injury it is biomechanics. Likely players like the Autrys are so fast that their cutting and running in highschool was just fun/easy for them. When the competition ramped up so did the stress on the ligament due to poor biomechanics. We've found than you can decrease the chance for reinjury greatly by reteaching the person how to run once they're able to. Unfortunately this isn't common practice and I'd be willing to bet most PTs in the country don't know/do this (in their defense the new therapies haven't become standard of care even in curriculum.) When I tore my ACL it was all about strengthening muscle and no attention was paid to how I run.
