The relationship between the tibialis posterior tendon and the accessory navicular

Out of a total of 116 cadaver feet, 29 specimens were selected by means of palpation of the tuberosity of navicular fur a possible presence of the acc essory navicular. They were then radiographed and the accessory navicular w as detected in ten. Also three fresh amputation specimens with an accessory navicular were added to the study. A total of 13 legs was dissected and in nine of them, the tibialis posterior tendon inserted directly into the acc essory navicular without extending to the sole of the foot. In these feet, the second part of the tibialis posterior tendon originated from the access ory navicular, extending to the normal insertions. There was no connection between these two parts and when traction was applied to either one, no mov ement was observed in the other. Also a fibrocartilaginous mass was detecte d in four specimens, probably formed to resist the friction between the ten don and the bone. These results may explain the pronated foot in the presen ce of the navicular, due to the lass of the function of the tibialis poster ior tendon.