Femoral head and neck fractures during the course of avascular necrosis are rare with only few reports in the English literature. Moreover, there are very few reports on an analysis of the patterns of these fractures. Four cases of femoral head fracture caused by minor trauma, which were quite different from the crescent fractures during the course of avascular necrosis were analyzed in regard to the underlying disease, causes, sites, types, directions, pattern of fractures and the injury mechanism of the fractures. The results are reported with special regard to the pattern of the stress fracture of the femoral head and neck during the course of avascular necrosis.