0 (zero phase)-lack of radiological signs;
I – clustery reorganization of bone structure, a linear osteosclerosis in subchondral regions, emergence of small edge osteophytes;
II – symptoms of phase I + more pronounced osteosclerosis – joint space narrowing;
III – pronounced subchondral osteosclerosis, large edge osteophytes, a significant joint space narrowing;
IV – grave massive osteophytes, the joint space is hardly traceable, the epiphyses of bones forming the joint are deformed with a dramatic increase in density.