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ACL Injury

Clinical Overview

Reviewed by Joseph Maloney, MD

A ligament is a tissue anywhere in the body that connects one bone to another. Four ligaments stabilize the knee joint and connect the femur to the tibia: the Posterior Cruciate Ligament, the Medial and Lateral Collateral Ligaments, and the Anterior Cruciate Ligament, or ACL. This report details what occurs when your ACL tears, either completely or partially. An injury to the ACL or any other ligament is known as a "sprain," or, more commonly, a "tear" when it is most severe.

The ACL runs from the back of the femur, or thighbone, to the front of the tibia, or shinbone, and prevents the tibia from moving too far forward. The most common mechanism of injury to the ACL is a twisting or cutting motion, which stretches or tears the ligament. The injury can happen in one of three "grades":

  • Grade 1, in which the ligament is stretched, but not torn.
  • Grade 2, where the ACL is partially torn.
  • Grade 3, in which the ACL is completely torn and instability, or looseness of the joint, occurs.

Depending upon the level of activity of the individual, an orthopedic surgeon may recommend operating or pursuing conservative methods to manage the ACL tear. An ACL tear is often accompanied by a tear of the Medial Collateral Ligament or meniscus.

Causes

  • Sudden deceleration
  • Awkward landings
  • A twisting injury. When the foot is planted and the body turns, the ACL is most susceptible to injury.
  • A direct blow to the leg from the front, such as a low tackle
  • Other injuries or accidents (such as an auto accident)


    Risk Factors
    "Cutting" (fast running and quick lateral movement) sports present the greatest risk for ACL injury (and other ligament injuries within the knee). Football, skiing, basketball, soccer and other sports are high-risk sports for ACL injuries. Also, previous ACL injuries or other serious knee injuries can be considered as risk factors for ACL damage.


    Last updated: May-16-07


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