Anterior cruciate ligament (ACL) injuries are quite common in the United States. About one in 3,000 people suffer from an ACL injury in their lifetime, and approximately 95,000 new cases of ACL injuries occur each year. Most of these injuries occur during sports that involve twisting, cutting, jumping and deceleration. Mechanisms that can cause an anterior cruciate ligament injury are excessive valgus stress (outside the knee), forced hyperextension, or forced external rotation of the femur on the fixed tibia (Evans, 2001). Many associate ACL tears with a strong impact or collision, however 80% of all ACL injuries are non-contact injuries. This statistic shows that ACL injuries are primarily caused by the individual himself rather than by an opponent or another person. The exact mechanism of non-contact ACL tears consists of incorrect knee positioning (e.g., landing with the knee extended) and a strong unopposed quadriceps contraction (Murray, 2013). Acute ACL injuries are classified based on the amount of damage done to the ACL. This damage varies from partial to complete rupture as well as whether or not other structures in the knee have been damaged. If only the ACL has been damaged, the injury is called isolated, however if more than the ACL has been damaged, it is called combined. Approximately 15% of all anterior cruciate ligament injuries are partial sprains (grade 1 or 2). Approximately 85% of all anterior cruciate ligament injuries are complete tears (grade 3). Only about 25% of ACL injuries are isolated, meaning that most of the time the ACL is also injured other structures in the knee. Some combined injuries may include damage to the meniscus (60%), articular cartilage (30%), and other knee ligaments (MCL, PCL, LCL) (30%). The extent of the damage done not only to the... center of the card... p, etc.). Natural grass fields are generally better than grass fields. They have lower rates of foot, ankle and knee injuries. Another type of risk factor identified is the type of shoes worn. Many studies have theorized that shoe design could increase the risk of anterior cruciate ligament (ACL) injuries. The two shoe factors that have attracted a lot of attention are the “release coefficient” and surface interaction. The “release coefficient” is the strength/weight ratio of the shoe. These studies stated that an optimal shoe should have minimal rotational friction, which would result in reduced rotational stress on the leg. It would also need maximum translational friction, which would allow for a safer stop. Both of these factors combined could potentially reduce anterior cruciate ligament injuries. Age is another important factor to consider when discussing factors that contribute to anterior cruciate ligament (ACL) injuries)..