Monarch Disease Ontology identifier MONDO_0017178 (osteochondritis dissecans) is a rare bone disease characterized by an acquired idiopathic necrotic lesion of subchondral bone with the formation of a sequestrum, which may detach to form loose bodies in joints. OCD mainly affects the knee, ankle and elbow joints and can lead to pain, functional limitations and secondary osteoarthritis. Also known as: Koenig disease, Konig disease, König disease, OCD, OD, osteochondritis dissecans (disease).