Anterior Cruciate Ligament Injury
What is it? An anterior cruciate ligament (ACL) injury is a partial or complete tear of the anterior cruciate ligament.
How does it present? The patient will usually present with an effusion that typically develops within the first few hours after the injury. Often the patient will have difficulty walking and have a sense of instability. An audible "pop" may have been heard at the time of injury. ACL tears may occur with contact or non-contact injuries, and many mechanisms such as hyperextension, rotation and varus or valgus forces can all be implicated. Non-contact injuries are more common in women.
Common exam findings: A large effusion is often present. A positive Lachman Test, Pivot Shift Test, or Anterior Drawer Test can be elicited on exam.
Tests and treatment: Knee x-rays may show a Segond's fracture, an avulsion fracture of the anterolateral margin of the lateral tibial plateau, and avulsion fracture of the tibial spine can be seen with ACL tears. A magnetic resonance imaging (MRI) should be ordered to evaluate anterior cruciate ligament integrity. Treatment in patients involved in activities requiring pivoting on the knee often requires surgical reconstruction. A conservative approach with rehabilitation and bracing may be attempted for other patients and the patient followed for evidence of knee instability.