Stress Roentgenographic Measurement for the Diagnosis of Rotational Instability of the Tibia in Posterior Cruciate Deficient Knees

Posterior sag and rotation of the tibia were studied in posterior cruciate deficient knees by using fresh cadaver knees. The tibia was internally rotated in both PCL deficient knees and in PCL deficient knees with associated posterior capsule or MCL injury. The tibia was externally rotated, contralaterally, in PCL deficient knees with associated LCL injury. The severity of the instability in posterior cruciate deficient and associated injury knees could be evaluated from roentgenographic measurement which we devised.