Isolated posterior cruciate ligament tear is most commonly caused by which mechanism?

Isolated posterior cruciate ligament tear is most commonly caused by which mechanism?

• A. Direct blow to the anterior tibia whilst knee is in flexion
• B. Hyperextension injury
• C. Valgus stress
• D. Tibial external rotation

Answer: (A)

The key idea is that the posterior cruciate ligament (PCL) prevents the tibia from moving backward (posteriorly) relative to the femur. When the knee is flexed, the PCL is taut, so a force that drives the tibia backward will stress and often tear it. A direct blow to the front of the tibia while the knee is bent (pushing the tibia posteriorly) is the classic mechanism that produces an isolated PCL tear. This aligns with the common dashboard-type injury, where a force hits the tibia with the knee flexed and pushes the tibia backward. Other mechanisms tend to injure different structures or cause more complex knee injuries. Hyperextension usually affects the ACL and anterior structures, valgus stress targets the Medial collateral ligament and related structures, and tibial external rotation is more commonly associated with other ligament injuries or combined injuries rather than isolated PCL tears.

The key idea is that the posterior cruciate ligament (PCL) prevents the tibia from moving backward (posteriorly) relative to the femur. When the knee is flexed, the PCL is taut, so a force that drives the tibia backward will stress and often tear it. A direct blow to the front of the tibia while the knee is bent (pushing the tibia posteriorly) is the classic mechanism that produces an isolated PCL tear. This aligns with the common dashboard-type injury, where a force hits the tibia with the knee flexed and pushes the tibia backward.

Other mechanisms tend to injure different structures or cause more complex knee injuries. Hyperextension usually affects the ACL and anterior structures, valgus stress targets the Medial collateral ligament and related structures, and tibial external rotation is more commonly associated with other ligament injuries or combined injuries rather than isolated PCL tears.