So, with all this talk of ACLs and MCLs and all these other CLs, we thought it might be helpful to give you a little bit of an idea of exactly what happened to Adrian Peterson's knee. Here's a helpful video to help you sort of visualize the whole thing.
What happened with Adrian Peterson is that he tore the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL) in his left knee.
The ACL is important because it keeps the knee from being pushed too far forward in relation to the femur, and it is generally injured by a twisting or bending of the knee, much like it was in Peterson's case.
The MCL keeps the knee from being bent open by too much force on the side of the knee.
Peterson has torn two of the four main ligaments that hold the knee together. The lateral collateral ligament (LCL) and the posterior cruciate ligament (PCL) are still intact, according to the reports we've gotten so far.
Hopefully this helps you to understand exactly what happened with Adrian Peterson's left knee.