The Lachman test is a clinical maneuver performed to assess the integrity of which structure?

• A. Posterior cruciate ligament
• B. Medial collateral ligament
• C. Anterior cruciate ligament
• D. Patellar tendon

Answer: (C)

The Lachman test checks the integrity of the anterior cruciate ligament by measuring how far the tibia can be pulled forward relative to the femur when the knee is bent just enough to place most of the ACL on tension. Position the knee in about 20–30 degrees of flexion, stabilize the femur with one hand, and gently translate the tibia forward with the other. A positive result is increased anterior translation of the tibia with a soft or absent end point, which indicates an ACL tear. If the end point is firm and the tibia doesn’t translate much, the ACL is likely intact. This test is particularly reliable in acute injuries because it minimizes hamstring guarding and isolates ACL function at this angle. The other structures aren’t evaluated with this maneuver: the posterior cruciate ligament is assessed with posterior tibial translation, the medial collateral ligament with valgus stress, and the patellar tendon is not the target of this test.