Which combination of maneuvers best distinguishes ACL from PCL tears?

• A. Anterior drawer and Lachman test suggest ACL; posterior drawer test suggests PCL.
• B. Posterior drawer test suggests ACL; anterior drawer and Lachman suggest PCL.
• C. Lachman test alone confirms ACL; anterior drawer confirms PCL.
• D. Anterior drawer alone confirms ACL; posterior drawer confirms PCL.

Answer: (A)

Tibial translation in the sagittal plane is what separates ACL from PCL injuries. The ACL resists forward (anterior) movement of the tibia relative to the femur, so tears produce increased anterior translation on tests like the Lachman and the anterior drawer. The PCL resists backward (posterior) tibial movement, so tears show increased posterior translation on the posterior drawer test. Because ACL injury shows up on both the Lachman and the anterior drawer, while PCL injury shows up on the posterior drawer, using those findings together best distinguishes between the two. In practice, positive anterior drawer and Lachman tests point to an ACL tear, whereas a positive posterior drawer points to a PCL tear.