Which finding is most specific for a PCL injury on exam?

Which finding is most specific for a PCL injury on exam?

• A. Increased anterior tibial translation on anterior drawer
• B. Increased posterior tibial translation on posterior drawer
• C. Increased varus laxity on varus stress test
• D. Increased valgus laxity on valgus stress test

Answer: (B)

The main idea is that a PCL injury specifically allows the tibia to move further backward relative to the femur when a posterior-directed force is applied. The PCL’s job is to prevent posterior tibial translation, so if it’s torn, the posterior drawer test—or simply noting increased posterior tibial translation—will be the most direct and sensitive sign of a PCL injury. Other exam findings point to different ligaments: increased anterior translation points to an ACL injury, while greater varus or valgus laxity indicates injury to the collateral ligaments or posterolateral corner. So, the finding of increased posterior tibial translation on the posterior drawer test is the most specific indicator for a PCL injury.

The main idea is that a PCL injury specifically allows the tibia to move further backward relative to the femur when a posterior-directed force is applied. The PCL’s job is to prevent posterior tibial translation, so if it’s torn, the posterior drawer test—or simply noting increased posterior tibial translation—will be the most direct and sensitive sign of a PCL injury.

Other exam findings point to different ligaments: increased anterior translation points to an ACL injury, while greater varus or valgus laxity indicates injury to the collateral ligaments or posterolateral corner. So, the finding of increased posterior tibial translation on the posterior drawer test is the most specific indicator for a PCL injury.