What is the function of the anterior cruciate ligament or ACL?

The anterior cruciate ligament (ACL) is essential for normal knee function and stability. The ACL attaches from the lateral femoral condyle (thigh bone) to the medial tibial plateau (shin bone) and prevents excessive anterior translation of the tibia on the femur (keeping the shin bone from moving too far forward), excessive internal rotation of the tibia (inward rotation of the shin bone), and knee hyperextension. The ACL also helps protect the knee from excessive valgus forces (bending the knee sideways toward the body), such as when a football player is tackled from the side. When the ACL is stretched or torn, the knee can feel very unstable and will oftentimes "give way," swell, and/or become painful.

The ACL (anterior cruciate ligament) prevents anterior (forward) movement of the tibia off of the femur, as well as hyperextension of the knee (a straightening movement that goes beyond the normal range of motion in the joint). By preventing these motions, the ACL provides stability to the knee joint and allows for dynamic motions.

This answer provided for NATA by Loras College.

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