"stage 0: normal joint"
"stage I: no skeletal abnormalities, soft-tissue swelling is present"
"stage II: osteoporosis and overgrowth of the epiphysis, no cysts, no narrowing of the cartilage space"
"stage III: early subchondral bone cysts, squaring of the patella, widened notch of the distal femur or humerus, preservation of the cartilage space"
"stage IV: findings of stage III, but more advanced; narrowed cartilage space"
"stage V: fibrous joint contractures, loss of the joint cartilage space, extensive enlargement of the epiphyses with substantial disorganisation of the joint"
"stage IV: findings of stage III, but more advanced; narrowed cartilage space"