The ACL stabilises the knee for reducing, twisting and leaping and pivoting action. The anterior cruciate ligament is in the center of your knee joint. Once you tear an ACL, you'll generally experience or listen to a pop, really feel the knee shift out of place and produce considerable swelling https://www.theorthopaedicandpainpractice.com/what-should-i-do-if-i-have-a-collateral-ligament-injury-of-the-knee/?_gl=1*xbbxlb*_up*MQ..&gclid=Cj0KCQjwkt6aBhDKARIsAAyeLJ2krYJSOuy5mZksrNqH-VDjQwW1ScD49yD8BUWysDG6u6bJPCSbXVUaAuCPEALw_wcB