Kohler's disease is due to osteonecrosis of:

B i.e. Tarsal boneRef: Fundamentals of Orthopedics, 2nd edition, Mohindra and Jain, Jaypee Publishers, page 44Explanation:Kohler's disease is osteochondritis of Navicula (a tarsal bone).In osteochondritis there occurs degeneration of osteochondral part of joint possibly due to a vascular etiology. However, exact etiology is unknown and the condition is categorized as under based on possible causative mechanisms.Types of OsteochondritisCrushing typeFreiberg's disease: Metatarsal heads.Kohler's disease: Navicula (Figure).Kienbock's disease Lunate.Parmer's disease. Capitulum.Scheuermann's disease: Ring epiphysis of vertebrae.Calve's disease: Central bony nucleus of vertebrae.Thiemann's disease: Phalangeal epiphysis.Traction/pulling typeOsgood-Schlatter's disease: Tibial tuberosity.Severe's disease: Calcaneal epiphysis.Johansson-Larson syndrome: Patellar ligament (at its lower pole patellar attachment).Iselin's disease: Base of fifth metatarsal.Adam's disease: Medial epicondyle of humerus.Splitting typeOsteochondritis dissecans.