TRANSFER OF MOVEMENT BETWEEN CALCANEUS AND TIBIA IN-VITRO

Excessive foot eversion and/or abnormal tibial rotation have been asso ciated with knee injuries. The mechanical coupling of leg and foot, wh ich may be related to the aetiology of knee injuries, is still not wel l understood. The goal of this study was to determine in vitro, as a f unction of loading and flexion position of the foot, the movement tran sfer from calcaneal eversion-inversion to tibial rotation and vice ver se occurring in the ankle-joint complex. A lower leg holding and loadi ng device with 6 degrees of freedom was used in the investigation. Fou rteen fresh-frozen, foot-leg specimens were tested. The movement trans fer from calcaneus to tibia and vice verse differed significantly betw een the specimens. The transferred movement was not the same for all i nput modes. Specifically, calcaneal eversion resulted in significant i nternal tibial rotation; however, internal tibial rotation did not ind uce any calcaneal eversion. Vertical loading of the tibia and foot fle xion position had a major influence on this movement transfer. The amo unt of calcaneal eversion transferred to internal tibial rotation depe nds on the individual mechanical coupling at the ankle-joint complex. Therefore excessive pronation, in running for instance, is only critic al for high knee loading when coupled with a high movement transfer in the ankle-joint complex. The interindividual differences may also sig nal difficulties for prosthesis design in total ankle-joint replacemen t and for the design of shoe orthotics.