Limited and frequently overlooked radiological evidence of knee osteoarthritis

Table 1 The 1986 American College of Rheumatology’s definition of knee osteoarthritis diagnosis

Clinical and laboratory	Clinical and radiographic	Clinical+
Knee pain + at least 5 of 9: Age > 50 years, stiffness < 30 minutes, crepitus, bony tenderness, bony enlargement, no palpable warmth, erythrocyte sedimentation rate (Westergren) < 40 mm/hour, rheumatoid factor < 1:40, synovial fluid signs of osteoarthritis (clear, viscous, or white blood cell count < 2000/mm3)	Knee pain + at least 1 of 3: Age > 50 years, stiffness < 30 minutes, crepitus, osteophytes	Knee pain + at least 3 of 6: Age > 50 years, stiffness < 30 minutes, crepitus, bony tenderness, bony enlargement, no palpable warmth
92% sensitive	91% sensitive	95% sensitive
75% specific	86% specific	69% specific

Alternative for the clinical category would be 4 of 6, which is 84% sensitive and 89% specific.