Just read that in TSN. Apparently, G Roberto Garza of the Bears has played the whole season without one also. I know you can run without ACLs but you can't move laterally. At least, that's what I heard and experienced myself.
IIRC, there are two ligaments at the back of the knee, in the form of a X. The ACL is one, and I believe the other is called the posterior cruciate ligament (PCL). Perhaps the PCL can compensate over time to have enough strength to stabilize the knee on its own. The lateral knee ligaments probably strengthen a lot in this situation, too.
Exactly how are they able to cut then?
Some things your body just needs more than others. It does "adapt" to some degree as well, but some things you can just get away without because they don't necessarily serve a critical function.You can live without a spleen without any SERIOUS issues. You can live without your tonsils and your appendix and your wisdom teeth without any issues at all.So if this was something you've had for awhile then your body adapts I suppose? This concept just blows me away.