Which physical examination maneuver is most specific for an ACL injury?

• A. Anterior drawer test
• B. Lachman test
• C. McMurray test
• D. Patellar grind test

Answer: (B)

The test that is most specific for an ACL injury is the Lachman test. The ACL prevents the tibia from moving forward relative to the femur, and performing the Lachman test with the knee only moderately bent (about 20–30 degrees) isolates the ACL's restraint. In this position, hamstring guarding and other joint factors have less influence, so a definite excessive forward translation of the tibia—or a soft/absent end-feel—most reliably indicates an ACL tear.

Other maneuvers assess different structures or are more prone to non-ACL factors: the anterior drawer test also checks anterior tibial movement but is less specific because it can be affected by hamstring guarding, swelling, or other ligament/muscle issues; the McMurray test targets meniscal pathology; the patellar grind test evaluates patellofemoral joint pain.