With the tibial drop back sign, one relies on gravity with the knee flexed to 90° to compare if there is any “dropping back” of the tibia on the injured side compared to the normal contralateral knee. In this test, one compares the prominence of the proximal tibia to the femoral condyles with the knee flexed to approximately 80°-90°. In the normal knee, the tibial plateau is located approximately 1 cm anterior to the femoral condyles. In a patient with a PCL tear, this prominence is diminished and there may be subluxation of the tibial plateau posterior to the femoral condyles in a severe PCL injury.