ACL injuries are multivariate by nature. Hip passive and active ranges of motion are simply one piece of the puzzle. I’ll outline more variables at play and steps we can take to reduce risk in future reviews. The role of the ACL is to prevent anterior translation of the femur against the tibia. It makes sense that larger hip internal and external ranges of motion would lower rates of ACL injury because being able to load the hips through a greater variety of movements should take stress off the ACL during compromised scenarios. If the leg has the ability to move through a larger ROM, we can reduce compressive forces upon the knee. If restrictions are present within the hip that decreases our ability to dissipate force across the knee, we will see increased force across the ACL. Basically, direct force transference due to “stiffness” in the hips across the ACL can be reduced by simply improving our hip internal and external rotation abilities.
One of my favorite ways to do this is the hip 90-90 drill. I find it especially useful as part of one of our post workout drills, or even programmed, as an auxiliary movement paired with our core lifts as it is not interfering or stressful. I’d recommend performing it for sets of ten reps or so on each side, progressively working through a larger range of motion as allowed.