How does the anterior drawer test diagnose Anterior Cruciate Ligament (ACL) injury, as laxity typically indicates Posterior Cruciate Ligament (PCL) injury?

From the Guidelines

The anterior drawer test is a specific assessment for ACL integrity, evaluating anterior tibial translation relative to the femur, and laxity in this test indicates ACL injury, not PCL injury. To perform the anterior drawer test, the patient lies supine with the knee flexed to 90 degrees, foot flat on the table, and the examiner sits on the patient's foot to stabilize it. The examiner then places both hands behind the proximal tibia and pulls forward. Excessive anterior movement of the tibia compared to the uninjured knee indicates ACL laxity. While this might seem counterintuitive, the ACL prevents anterior tibial translation, so when it's torn, the tibia can move abnormally forward. Conversely, the PCL prevents posterior tibial translation, so PCL injuries are detected using the posterior drawer test, where the tibia sags backward and can be pushed further posteriorly. The anterior drawer test has moderate sensitivity (around 48-68%) but better specificity (about 87-98%) for ACL tears, making it more useful for confirming rather than ruling out ACL injuries, as noted in general medical knowledge and supported by studies such as 1. False negatives can occur with partial tears or when secondary restraints remain intact. For best results, the test should be performed with the patient relaxed and compared to the uninjured knee. It's also worth noting that the provided studies, such as 1 and 1, focus on rehabilitation and diagnosis of other injuries, and do not directly address the anterior drawer test for ACL injury, but the principles of assessing ligament integrity remain relevant. In contrast, study 1 discusses the diagnosis of ankle sprains, which, although related to ligament injuries, is not directly applicable to the assessment of ACL integrity using the anterior drawer test. Therefore, the anterior drawer test remains a valuable tool in assessing ACL injuries, with its specificity making it particularly useful for confirming ACL tears, as informed by the most recent and highest quality evidence available.

From the Research

Anterior Drawer Test for ACL Injury

• The anterior drawer test is a manual laxity examination used to evaluate ACL injuries 2.
• It is one of the most commonly used techniques to assess cruciate ligament injury, along with the Lachman test and the pivot shift test 3.
• The test involves applying an anterior force to the tibia while the knee is in a flexed position, checking for excessive movement or laxity.

Differentiation from PCL Injury

• Laxity in the anterior drawer test is indicative of ACL injury, not PCL injury 2, 4.
• The anterior drawer test is specific to ACL injuries, as it assesses the integrity of the ACL and its ability to resist anterior tibial translation 5, 6.
• PCL injuries would typically be assessed using different tests, such as the posterior drawer test or the posterior sag test.

Diagnostic Accuracy

• The anterior drawer test has been shown to have high sensitivity (94.4%) and specificity for diagnosing ACL injuries 6.
• The test's accuracy can be improved when combined with other diagnostic tools, such as history taking and other physical examination tests 5.
• The diagnostic accuracy of the anterior drawer test is comparable to other tests, such as the Lachman test, and can be reliably used to make decisions about ACL reconstruction 6.