[New experimental data for the classification of knee instabilities]

Combined instabilities of the knee are usually expressed in compartmental terms. Several clinical evaluation forms result from these classification systems. We performed an experimental study on forty fresh cadaver knees to relate abnormal femorotibial motion with the corresponding structural damage. Translational forces were introduced to the testing apparatus while the tibia was allowed to rotate. In anteromedial lesions (ACL, MCL, POL) the "envelope of motion" was not pronounced in the anteromedial direction. There was only little difference in the amount of the anterior drawer with the foot in external rotation or left free to rotate. Posterolateral lesions (PCL, LCL, Popliteus tendon) were related to posterolateral laxity in 90 degrees of flexion. At 20 degrees of flexion laxity was found to be the greatest.