Association of slipped upper femoral epiphysis and peroneal spastic flatfoot.

A significant association between slipped upper femoral epiphysis (SCFE) and subtalar arthritis causes peroneal spastic flatfoot. Three patients with this association were observed in 136 cases of SCFE, an incidence of 2.3%; the anticipated incidence would be 0.4%. We postulate that both conditions reflect an underlying immunologic disorder.