The anterior cruciate ligament (ACL) is located in the knee. Its main function is to prevent the tibia from excessively moving forward. The ACL is the most commonly injured ligament in the knee. In fact, it is responsible for about 60% of all knee injuries, and it most often get injured during athletic activities. It is usually caused by one of two mechanisms of injuries. The first one is a hard hit to the lateral side of the knee, which causes the ACL to stretch and possibly tear. Similar to the first mechanism, the second one is when the foot is planted and the leg, along with the rest of the body, turns or twists. For example, a soccer player may plant his cleats into the ground while trying to make a sharp turn therefore causing the ACL to stretch or even tear just as...