Which test is the most sensitive for ACL injuries?

Which test is the most sensitive for ACL injuries?

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

Answer: (B)

The most sensitive cue for an ACL tear comes from how the knee is positioned to test anterior tibial translation. When the knee is bent about 20–30 degrees, the ACL is under the greatest anterior restraint, so pulling the tibia forward while stabilizing the femur isolates the ACL's integrity. If the ACL is torn, you’ll detect noticeable anterior laxity with a softer or absent endpoint. This position also minimizes the influence of surrounding tissues and reduces hamstring guarding that can mask instability, making even smaller tears more detectable. Because of these factors, this test has the highest sensitivity for acute ACL injuries. Other tests perform the assessment differently. The anterior drawer test, done with the knee at about 90 degrees, can be more easily affected by hamstring contraction and swelling, so it’s less sensitive for isolated ACL tears. The pivot shift test assesses dynamic instability and is valuable but highly technique-dependent and often less reliable in the acute setting. The varus stress test targets the lateral collateral complex, not the ACL, so it isn’t used to evaluate ACL integrity.

The most sensitive cue for an ACL tear comes from how the knee is positioned to test anterior tibial translation. When the knee is bent about 20–30 degrees, the ACL is under the greatest anterior restraint, so pulling the tibia forward while stabilizing the femur isolates the ACL's integrity. If the ACL is torn, you’ll detect noticeable anterior laxity with a softer or absent endpoint. This position also minimizes the influence of surrounding tissues and reduces hamstring guarding that can mask instability, making even smaller tears more detectable. Because of these factors, this test has the highest sensitivity for acute ACL injuries.

Other tests perform the assessment differently. The anterior drawer test, done with the knee at about 90 degrees, can be more easily affected by hamstring contraction and swelling, so it’s less sensitive for isolated ACL tears. The pivot shift test assesses dynamic instability and is valuable but highly technique-dependent and often less reliable in the acute setting. The varus stress test targets the lateral collateral complex, not the ACL, so it isn’t used to evaluate ACL integrity.