[Pronation from the viewpoint of the transfer of movement between the calcaneus and the tibia]

Excessive foot eversion and abnormal tibial rotation have been associated with knee injuries. Why and whether or not overpronation in athletes leads to overuse injuries at the knee joint, however, is still not understood. It could be that this is related to the mechanical coupling at the ankle joint complex. The purpose of this study was to quantify the movement transferred from calcaneal eversion-inversion into tibial rotation, and vice-versa from tibial rotation into calcaneal eversion-inversion. Fourteen foot-leg specimens were used for investigation. A holding device with six degrees of freedom was constructed which allowed to rotate the calcaneus and to determine the resulting tibial rotation, and vice-versa. The movement transfer between calcaneus and tibia varied substantially, and it was not the same for both input modes. In the case of applied internal tibial rotation no calcaneal eversion was found. Apparently, the movement transfer depends from the individual mechanical coupling at the ankle joint complex. Excessive calcaneal eversion does only result in excessive rotational loading of the knee joint when coupled with a high movement transfer at the ankle joint complex. Finally, the results imply that, during gait, pronation results from ground reaction forces acting on the calcaneus, since internal tibial rotation is not transferred into calcaneal eversion.