Which ACL test is performed with the knee in about 20-30 degrees of flexion to assess anterior laxity?

Which ACL test is performed with the knee in about 20-30 degrees of flexion to assess anterior laxity?

• A. Lachman
• B. Anterior Drawer
• C. Pivot Shift
• D. Posterior Drawer

Answer: (A)

Lachman test isolates the ACL by assessing how far the tibia can be translated anteriorly when the knee is in a light bend, about 20–30 degrees. In this range the ACL is taut and acts as the main restraint to forward movement of the tibia, while the hamstrings are less likely to mask laxity. If the ACL is torn, you’ll feel increased anterior translation and a soft or absent end-feel, indicating anterior laxity. Other tests target different aspects: the anterior drawer uses a larger bend (around 90 degrees) and can be influenced by hamstring tension and other structures, making it less specific for isolated ACL damage. The pivot shift checks for dynamic, rotary instability of the knee, not just straight-ahead laxity. The posterior drawer evaluates the opposite cruciate ligament, the PCL, with posterior rather than anterior tibial movement.

Lachman test isolates the ACL by assessing how far the tibia can be translated anteriorly when the knee is in a light bend, about 20–30 degrees. In this range the ACL is taut and acts as the main restraint to forward movement of the tibia, while the hamstrings are less likely to mask laxity. If the ACL is torn, you’ll feel increased anterior translation and a soft or absent end-feel, indicating anterior laxity.

Other tests target different aspects: the anterior drawer uses a larger bend (around 90 degrees) and can be influenced by hamstring tension and other structures, making it less specific for isolated ACL damage. The pivot shift checks for dynamic, rotary instability of the knee, not just straight-ahead laxity. The posterior drawer evaluates the opposite cruciate ligament, the PCL, with posterior rather than anterior tibial movement.