The ACL, or anterior cruciate ligament, works in tandem with the PCL (posterior cruciate ligament) to create the back-and-forth motion your knee makes. The ACL acts as the glue that holds the knee together, keeping it stable. Without this crucial ligament in your knee, you wouldn’t be able to stand because there wouldn’t be anything there to hold and help stabilize your bones and keep you from falling to the ground.
The ‘Rubber Band’ Analogy
Imagine your knee as a set of four rubber bands: two on the outside and inside of your knee and two that overlap one another to create an “x” shape. All of these “rubber bands” work together to help the knee move freely.
A rubber band stretches and contracts to hold things together, just like your ACL does. You may put a rubber band around a bundle of pencils to hold them together, and your ACL holds your tibia and fibula together, keeping them from sliding out of place.
As time passes, the rubber band loses its springiness with more and more stretching, twisting, and just general use. The more times your use that rubber band to hold together a set of papers, the less tight that hold gets. This is similar to your ACL. With more and more use, the bond that your ACL has with your knee can become weak due to overuse.
One day you may go to put that rubber band around that set of papers and it snaps because it couldn’t handle the pressure, the same can happen with your ACL. You may go out one day for a run, fall, and tear your ACL. An ACL tear or ACL sprain can prevent you from being able to put any weight on the affected knee without it buckling.
Many people think of ACL injuries and instantly relate them to sports. That isn’t always true though, as roughly 30% of all ACL injuries occur outside of sports settings, according to the Department of Orthopedic Surgery at the University of California. While a majority of ACL injuries occur in sports, it’s still important to take care of your “rubber bands” in everyday life.