Excessive posterior translation during a knee posterior drawer test indicates injury to which structure?

• A. PCL injury
• B. ACL injury
• C. MCL injury
• D. LCL injury

Answer: (A)

The test assesses posterior stability of the knee and the integrity of the posterior cruciate ligament, which is the primary restraint to backward movement of the tibia. When the tibia translates rearward excessively under a posterior force (with the knee typically flexed around 90 degrees), it indicates the PCL is damaged or lax. The ACL mainly prevents forward (anterior) tibial movement, so its injury would more likely show increased anterior translation, not posterior. The MCL and LCL stabilize the knee against side-to-side forces, so injuries to those ligaments don’t primarily produce excessive posterior tibial movement. Thus, an excessive posterior translation on the posterior drawer test points to a PCL injury.