The load bearing joints of the human body and particularly the ankle are often seriously damaged because of different pathological events. During the last 10 years a lot of total ankle prostheses have been studied and implanted, in consequence of the inadequate results obtained by arthrodesis (i.e. the fusion of the joint). The aim of this paper is to analyze mechanical features (functional, kinematic, and strength) of the ankle joint in order to provide optimized design criteria of an arthroprosthesis substituting the disabled joint.