[The functional anatomy of the lower extremity, especially the foot].

The skeletal elements as well as the muscles of the human foot are functionally adapted to bearing body load. The arrangement of the hindfoot bones is essential for establishing the longitudinal foot arch. This and the transverse arch, too, must be supported by the passively acting plantar ligaments and the active plantar muscles. The total muscle force is needed for support to 80%; 20% will serve for articular mobility. Insufficiency or loss of stabilizing factors will lead to unphysiological high stress of the skeletal elements. In consequence, the arch system will be weakened and stress fractures may occur.