Which test is most sensitive for an ACL tear?

Which test is most sensitive for an ACL tear?

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

Answer: (B)

The key idea is sensitivity—which exam best reveals an ACL tear when one is present. The Lachman test, performed with the knee flexed about 20–30 degrees, isolates the ACL and measures anterior tibial translation with minimal interference from the hamstrings or surrounding structures. This position makes even partial ACL tears noticeable, so it detects more true positives than the other tests. The anterior drawer test is useful but at 90 degrees of flexion it can be less sensitive because hamstring guarding and other factors can mask laxity. The pivot shift test reflects dynamic instability and is highly specific, but its sensitivity is lower and it’s more technique-dependent, especially in acute injury. The McMurray test targets meniscal pathology, not the ACL, so it isn’t appropriate for assessing ACL tears. So, the Lachman test is the best option for identifying an ACL tear due to its higher sensitivity in isolating ACL laxity.

The key idea is sensitivity—which exam best reveals an ACL tear when one is present. The Lachman test, performed with the knee flexed about 20–30 degrees, isolates the ACL and measures anterior tibial translation with minimal interference from the hamstrings or surrounding structures. This position makes even partial ACL tears noticeable, so it detects more true positives than the other tests.

The anterior drawer test is useful but at 90 degrees of flexion it can be less sensitive because hamstring guarding and other factors can mask laxity. The pivot shift test reflects dynamic instability and is highly specific, but its sensitivity is lower and it’s more technique-dependent, especially in acute injury. The McMurray test targets meniscal pathology, not the ACL, so it isn’t appropriate for assessing ACL tears.

So, the Lachman test is the best option for identifying an ACL tear due to its higher sensitivity in isolating ACL laxity.