Grade 2 sprains occur when the ligament is stretched to the point that it becomes loose; this is also referred to as a partial tear. Grade 3 sprains occur when the ligament is completely torn into two pieces, and the knee joint is no longer stable. This is the most common type of ACL injury.Around half of ACL injuries occur in conjunction with injury to other structures in the knee, including the other ligaments, menisci, or cartilage on the surface of the bones. A specific pattern of injury called the "unhappy triad" (also known as the "terrible triad," or "ODonoghues triad") involves injury to the ACL, MCL, and medial meniscus, and occurs when a lateral force is applied to the knee while the foot is fixed on the ground. Prevention
Interest in reducing non-contact ACL injury has been intense. The International Olympic Committee, after a comprehensive review of preventive strategies, has stated that injury prevention programs have a measurable effect on reducing injuries. These programs are especially important in female athletes who bear higher incidence of ACL injury than male athletes, and also in children and adolescents who are at high risk for a second ACL tear.Researchers have found that female athletes often land with the knees relatively straight and collapsing inwards towards each other, with most of their bodyweight on a single foot and their upper body tilting to one side; these four factors put excessive strain on the ligaments on the knee and thus increase the likelihood of ACL tear.
Norco may refer to:

Places
Norco, California, U.S.
Norco Hills, or La Sierra Heights, section of the Temescal Mountains
Norco, Louisiana, U.S.

Other uses
Norco Bicycles, a Canadian bicycle manufacturer
Norco Co-operative, an agricultural supply and marketing co-operative, New South Wales, Australia
Northern Co-operative Society (Norco), a defunct Aberdeen, Scotland co-operative society
Norco, a brand name for the fixed-dose combination opioid pain medication hydrocodone/paracetamol
NORCO (video game), a point-and-click video game set in a fictional version of Norco, Louisiana

See also
Norco shootout