Which test is most sensitive for diagnosing an ACL tear?

• A. Lachman test
• B. Anterior drawer test
• C. Pivot shift test
• D. Posterior drawer test

Answer: (A)

Detecting ACL tears relies on tests that reveal anterior tibial translation when the knee is positioned to minimize hamstring influence. The Lachman test does this best by placing the knee about 20-30 degrees of flexion and applying an anterior pull on the tibia. In an ACL-deficient knee, the tibia shows increased forward movement and a soft or absent endpoint, making this test highly sensitive even when swelling or muscle guarding is present.

The anterior drawer test, done at 90 degrees of flexion, is more affected by hamstring contraction and joint effusion, which can hide the laxity and reduce sensitivity, especially early after injury. The pivot shift test looks at dynamic, rotary instability and, while informative and fairly specific, is technically demanding and less reliably sensitive across examiners. The posterior drawer test targets the PCL, not the ACL, so it isn’t used to diagnose ACL tears. So the Lachman test is the best choice for sensitivity in ACL injury detection.