Osteochondritis dissecans (OCD) is considered to show the following stages of pathological progression: IA, nearly normal-cartilaginous; IB, deteriorated-cartilaginous; IIA, cartilage-ossifying; and IIB, cartilage-osteonecrotic. However, the validity of this pathological staging for OCD has yet to be confirmed in a large number of cases.
Source: JSES