Necrotizing cystic degeneration refers to a condition in which there is destruction of bone and osteonecrosis. This condition appears on plain films as a localized increase in bone density, i.e., a hyper-translucent shadow with a clear boundary between normal bone and necrotic bone in the form of a mass, and is therefore clinically referred to as a bone cystic lesion. In the process of osteoarthritis, if there is a cystic change in the bone, it indicates that the articular cartilage inside the joint has been severely damaged, and the bone under the cartilage is being destroyed and necrosis is occurring, and the next step is to produce significant osteophytes, deformation of the joint, and narrowing of the joint space. In the onset of osteonecrosis, once the cystic degeneration of the bone is produced, it suggests that the shape of the bone will immediately collapse. In this period, it is still the early stage of osteonecrosis, and if treated early, it can lead to a better prognosis of osteonecrosis. However, if delayed, there is a risk of bone contour changes and complications such as osteoarthritis.