The anterior cruciate ligament (ACL) is important for maintaining stability of the knee joint, particularly in activities involving weaving, pivoting or kicking. The knee becomes unstable with a ruptured ACL and the joint may become more damaged over time. ACL reconstruction is the surgical treatment of choice to restore stability at the knee joint.
https://www.physio-pedia.com/Anterior_Cruciate_Ligament_(ACL)_Reconstruction