ANATOMY - Anterior Crucitate Ligament (ACL)

The anterior cruciate ligament (ACL) is a ligament that connects the tibia to the femur. It serves to prevent the tibia (leg) from moving forward relative to the femur (thigh). The ACL is in the center of the knee. It crosses the PCL, hence the name, cruciate.

How does someone injure the ACL?

This ligament is frequently injured in contact sports (e.g., football) and pivoting sports (such as soccer and skiing), however there are many scenarios for injury to this ligament. Usually the patient complains of a sudden injury to the knee and the inability to walk right after the accident. Often, there is a significant amount of swelling that occurs relatively soon after the injury. In contact sports (e.g., football) the injury typically occurs when another player impacts the side of the knee. Non-contact ACL injuries are more common in women, such as a female soccer player who suddenly changes direction and feels a pop in her knee.

What are the symptoms of an ACL injury?

Torn ACL

Initially, the symptoms are pain and fairly immediate swelling. Often patients will complain of hearing a loud "pop", which is the sound of the actual ligament tearing.

After the pain and swelling resolve, patients complain of episodes of instability, or giving-way. The knee feels loose. Some people liken this to walking on rollerskates. For some people, this looseness is predictable; other people live in fear of their knee giving out because they are unable to predict the motions that cause the instability.

What happens after the ACL injury?

It depends on the severity of the injury and whether there are any other associated injuries, such as a medial collateral ligament tear or a meniscal tear. Often the swelling resolves after a couple of weeks. Some patients will be able to function without any problems after they get over the initial injury, especially if they had only a partial tear. The majority, however, will notice "instability"; the feeling that their lower leg is shifting forward on their thigh bone. For some, this will be a minor nuisance; for others, it will be a significant disability.

To learn about the treatment of ACL tears, click Next below:

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