"stage I: pre-radiological stage with normal radiographs but CT or MRI osseous changes present"
"stage II: osteoporosis, sclerosis, or both, or localised subchondral osteolysis without fracturing"
"stage III: subchondral fracture with mild loss of congruity and a “crescent sign”"
"stage IV: extensive collapse of subchondral bone with severe articular incongruity and secondary degenerative changes (osteochondral flaps may break free and become loose bodies)"
"stage V: stage IV humeral head changes with pathologic changes of the glenoid"
"stage I: pre-radiological stage with normal radiographs but CT or MRI osseous changes present"