The COP sway induced by knee flexion in one-leg stance with maximal heel loading was observed in the group of 43 persons (86 cases). The measurement was conducted on Footscan system, the data and the hypotheses statistical testing were processed in Excel programme using the t-test, correlation and χ2-test. During the knee flexion in the one-leg stance with the maximal heel loading there was evidenced the transversal COP sway (p<0.001) mostly in medial direction (p<0.001). Regarding the limited possibility of the loading on the first metatarsal head (while the maximal heel loading), that COP sway can be considered as a result of the calcaneus pronation/inversion, thus subtalar joint movement. A sway in anteroposterior axis comes along with (p<0.001), but without prevalence in one or the other direction. Only along with an atypical lateral COP sway there comes posterior sway almost every time (p<0.01), but despite of it, during posterior sway there is medial sway along with in the most frequently (p<0.005). The results support the relation between knee and ankle movements in closed kinematic chain observed by physical examination, which is determined by mutual position of joint axes.

        Key words: pronation, eversion, closed kinetic chain, COP