Also known as Morbus Köhler 2, Freiberg disease or Freiberg infraction. It is a form of avascular necrosis in the metatarsal bone of the foot. It generally develops in the second metatarsal, but can occur in any metatarsal. Physical stress causes multiple tiny fractures where the middle of the metatarsal meets the growth plate. These fractures impair blood flow to the end of the metatarsal resulting in the death of bone cells (osteonecrosis). It occurs mainly in girls between the ages of 12 and 18.