Radiographic measurement of femorotibial rotation in weight-bearing - The influence of flexion and extension in the knee on the extensor mechanism and angles of the lower extremity in a healthy population

Purpose: A system for examination and measurement of the weight-bearing kne e was developed earlier on examination equipment used for QUESTOR Precision Radiography (QPR), adapted to computed radiography and to a picture archiv ing and communication system. In this study the same system was used to dev elop a method to define "patellar variables" including measurements of the rotation of the femur and the tibia and the patellar translation, between s emiflexion and extension, as well as the Q-angle. The aim of this study was to evaluate the reproducibility of these patellar variables and also to es tablish "normal" reference values for both the patellar variables and the v ariables in the original QPR system. Material and Methods: For evaluation of the reproducibility 10 volunteers w ith healthy knees were examined twice. To obtain the reference values, 80 v olunteers with healthy knees, 10 females and 10 males within each decade be tween 20 and 59 years of age, were examined. Results and Conclusion: The reproducibility of the rotation of the femur an d the tibia and of the Q-angle was 2-3 degrees (SD) and of the patellar tra nslation about 3 mm (SD). The result from the healthy volunteers will be a useful tool for evaluation of disorders in the knee joint.