Side differences in the anatomy of human knee joints.

Side-to-side comparison of anatomical or functional parameters in the evaluation of unilateral pathologies of the human knee joint is common practice, although the amount of symmetry is unknown. The aim of this study was to test the hypothesis that there are no significant differences in the morphometric knee joint dimensions between the right and the left knee of a human subject and that side differences within subjects are smaller than intersubject variability. In 20 pairs of human cadaver knees, the morphometry of the articulating osseous structures of the femorotibial joint, the cruciate ligaments, and the menisci were measured using established measurement methods. Data were analyzed for overall side differences and the ratio between within-subject side differences and intersubject variability was calculated. In three out of 71 morphometric dimensions there was a significant side difference, including the posterior tibial slope, the anatomical valgus alignment of the distal femur, and the position of the femoral insertion area of the ACL. In two additional parameters, including the cross-sectional area of the ACL and PCL, within-subject side differences were larger than intersubject variability. In general, there was a positive correlation in morphometric dimensions between right and left knees in one subject. It is concluded that a good correlation in the morphometric dimensions of a human knee joint exists between the right and the left side. This study supports the concepts of obtaining morphometric reference data from the contralateral uninjured side in the evaluation of unilateral pathologies of the knee joint.