The anterior cruciate ligament (ACL) is 1 of 4 main ligaments in the knee. Ligaments are rope-like structures that connect and hold the bones together to keep the knee stable. The ACL, along with the posterior cruciate ligament (PCL), is located in the center of the knee.
The ACL is one of the primary ligaments providing stability to the knee and, therefore, is one of the most commonly injured knee ligaments.
The ACL and PCL are called cruciate ligaments because they form a cross in the middle of the knee joint. These two ligaments fit perfectly together in a space called the intercondylar notch. Notch size varies between people. Since the ACL and PCL completely fill the notch, people with larger notches have larger ligaments. People with smaller notches have smaller ligaments and are more susceptible to ACL tears.
Along with providing stability to the knee during sports-related activities, the ACL and PCL help center weight through the knee joint, minimizing wear and tear on other parts of the joint.