With the present thesis, a body model for clinical gait analysis was initially designed and evaluated on the basis of 25 subjects. A reduction of measurement errors for gait parameters and a more accurate determination of the knee joint axis compared to the conventional model could be detected. The gait of 14 patients with varus malalignment of the knee 12-19 years of age and 15 healthy control subjects were analyzed in a second experimental study. Varus malalignment occur concomitantly with biomechanical changes in gait pattern in the sagittal, frontal, and transverse plane. These findings imply that varus malalignment of the knee should not be viewed as an isolated problem in the frontal plane. Threedimensional gait analysis is therefore a diagnostic tool that can be used to gain a better understanding of the relationship between joint loading and the onset or progression of articular cartilage degeneration in patients with varus malalignment of the knee.