The anterior cruciate ligament, or ACL, is the most often injured part of the knee. The ACL supports many actions commonly performed in sports, like stopping suddenly and changing direction quickly. The transition from sprinting at high speed to making a sudden stop can overstress the ACL, which over time can lead to serious injury.

So what is the ACL? To explain: “anterior” means “before” or “in front,” and “cruciate” means “overlapping” or “crossing,” so the ACL is the ligament that crosses in front of the knee. It holds the knee together in concert with three other knee ligaments: the PCL (“posterior,” or behind the knee); the MCL (“medial,” or in the “middle” of the knee); and the LCL (“lateral,” or on the “side” of the knee). The ACL stops the tibia from sliding forward during movement. All four knee ligaments are essential to protect the knee during movement—everything from standing up to all-out sprinting.
The best way to prevent ACL injuries is to use proper running form and correct techniques for stopping and changing direction. The knee is like a brake pad on a car. If you want your brake pads to last longer, you stop gradually at red lights instead of slamming on the brakes. The knee works the same way. When you are running, start your stopping motion earlier and avoid keeping your weight too far forward. “Slamming on the brakes” or stopping too quickly, wears down the cartilage and puts more stress on the knee ligaments, increasing the chance of injury.
Check out STACK’s ACL guide to learn more about preventing and recovering from an ACL injury.
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