An anterior cruciate ligament (ACL) injury is a tear in the knee ligaments that join the upper leg bone and the lower leg bone. This ligament is the one responsible for keeping the knee stable. ACL injuries may range from mild to severe and, if not treated, may lessen the ability to control knee movement and cause the bones to rub against each other.
The ACL can be injured if the knee joint is bent backward, twisted, or bent side to side. However, there is a greater possibility of injury if any of these movements happen at the same time. This type of injury usually occurs during sports. It happens when the athlete’s foot is firmly planted on the ground and a force suddenly hits the knee while the leg is straight or bent. It can also happen when there is a rapid change in direction, a sudden slowing down while running, or a bad landing from a jump.
Symptoms may include a popping sound or sensation in the knee when the injury occurs, pain on the outside and at the back of the knee, swelling in the knee during the first hour of the injury, or pain or swelling that may cause limited knee movement.
There are three treatment goals an orthopedic surgeon usually suggests: to make the knee stable, to make the knee strong enough, and to reduce the chance of more damage.