Lateral radiograph of knee with posterior cruciate ligament (PCL) injury

The image on the left (A) is a lateral radiograph of an uninjured knee. A line drawn along the anterior border of the tibial shaft intersects with the medial femoral condyle, demonstrating the absence of any posterior displacement. The image on the right (B) is a lateral radiograph of a patient with a posterior cruciate ligament (PCL) tear and demonstrates posterior displacement of the tibia. Note the disparity indicated by the arrow between the posterior line drawn along the tibial shaft and the anterior line drawn along the anterior aspect of the medial femoral condyle.