Early diagnosis and targeted intervention based on the pathogenesis of rapidly progressive osteoarthritis of the hip

Table 1 Summary of classification system for rapidly progressive osteoarthritis of the hip

Ref.	Classification	Description	Follow-up period
Irwin and Roberts[6], 1998	Rapid	Chondrolysis for about 18 months followed by bone loss of 10-15 mm/year	> 18 months
	Moderate	Chondrolysis for 18-30 months followed by bone loss at 5-10 mm/year	> 18-30 months
	Delayed	Normal progression for 3-5 years after initial symptoms, then sudden change to rapid or moderate patterns	> 3-5 years
Pivec et al[3], 2013	Type 1	Rapid joint space narrowing, no rapid femoral head dissolution or acetabular bone loss	> 12 months
	Type 2	Severe joint degeneration, rapid progression with femoral head and acetabular destructive changes within 6-18 months	6-18 months
Zazgyva et al[2], 2017	Grade 1	Partial joint space narrowing; no deformation/ascension of the femoral head	> 3.5 years
	Grade 2	Complete disappearance of the joint space; deformed femoral head and acetabulum; femoral head ascension ≤ 0.5 cm above radiological teardrop	> 3.5 years
	Grade 3	Complete disappearance of the joint space; partial osteolysis of the femoral head; femoral head ascension > 0.5 cm above radiological teardrop	> 3.5 years
Yasuda et al[9], 2020	Type 1	Joint space narrowing with no femoral head destruction within 12 months after onset of hip pain	< 12 months
	Type 2	Rapid joint space narrowing and femoral head destruction within 12 months after onset of hip pain	< 12 months