Table 1.

Radiographic findings differentiating between primary osteoarthritis, osteonecrosis, and rapidly progressive osteoarthritis [4••]

Diagnosis	Plain radiographic findings
Primary OA	• Osteophyte formation • Subchondral cysts • Joint space narrowing • Sclerosis
Rapidly progressive OA	• Joint space narrowing without acetabular bone loss or femoral head collapse
ON	• Femoral head collapse • Subchondral fracture • Acetabular bone loss and degeneration in latest stages

OA osteoarthritis, ON osteonecrosis