Identifying the Effects of Knee Anatomy Variation on the Envelope of Knee Motion (Varus-Valgus) Using Principal Components

The motion patterns of the human knee joint depend on its passive motion characteristics, which are described by the ligamentious and articular constraints. Since active motions, like walking and squatting are believed to fall within a passive envelope, the basis for the understanding of the knee joint kinematics lies in the description of its passive constraint characteristics [1]. Although several authors studied passive envelope characteristics of a knee, it is not clear from the literature which anatomical structures guide the knee in passive or active motion and how their geometric arrangement produces the unique path of passive knee motion [1–3]. A few mathematical models have been developed to study the structures that guide the passive knee motion [1, 2]. However, their hypotheses were not supported by a sufficiently detailed ligament bundle model, soft tissue properties, ligament insertion-origin sites and their intra-subject variability. To explain the relationship between knee anatomy and its variability with three-dimensional knee motion completely, new methodology must be developed. The objective of the present study was to estimate the effects of variation in knee anatomical factors on the tibiofemoral passive envelope using a multivariate analysis technique, principal component (PC) analysis.