What is a common mechanism of injury for a PCL tear?

• A. MVA dashboard injuries
• B. Falling onto a fully flexed knee during sports
• C. Direct blow to the anterior tibia with the knee extended
• D. Hyperextension injury without posterior tibial translation

Answer: (A)

A PCL tear most often happens when the tibia is driven backward relative to the femur, placing a sudden posterior load on the ligament. In the classic dashboard injury from a car crash, the knee often hits the dashboard with the knee slightly flexed, forcing the tibia to translate posteriorly and tearing the PCL. This mechanism directly exploits the PCL’s job of preventing posterior tibial movement, making it the most common and recognizable cause.

Falling onto a fully flexed knee can also injure the PCL due to posterior translation of the tibia, but dashboard injuries are the prototypical scenario examiners look for. A direct blow to the anterior tibia with the knee extended would not typically create the same posterior tibial translation pattern that loads the PCL, and hyperextension injuries can involve multiple structures rather than primarily stressing the PCL.