Which physical examination test is most sensitive for detecting an ACL tear?

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

Answer: (D)

The test that best detects an ACL tear relies on how much the tibia can translate forward relative to the femur when the knee is in a position that isolates the ACL. The Lachman test uses about 20–30 degrees of knee flexion, with the femur stabilized and the tibia gently pulled forward. In a normal knee, the ACL restrains that forward movement and a firm end-feel is felt. If the ACL is torn, there is markedly increased anterior translation and a softer or absent end-feel. This position minimizes the influence of hamstring muscles and other structures, making even partial tears easier to pick up.

Other tests have their uses—an anterior drawer test, done at 90 degrees of flexion, can be less sensitive because hamstring guarding and other restraints can obscure laxity; the pivot shift test looks for dynamic instability during rotation and is more technique-dependent and specific but less consistently sensitive; the McMurray test targets meniscal pathology rather than ACL integrity. So, the Lachman test most reliably reveals ACL deficiency, especially in acute injuries.