Table 3.

ACR clinical classification criteria for knee OA [28].

Clinical and laboratory	Knee pain and at least 5 of 9	Age > 50 y Stiffness < 30 min Crepitus on active motion Bony tenderness Bony enlargement No palpable warmth of synovium Erythrocyte sedimentation rate < 40 mm/h Rheumatoid factor < 1:40 Synovial fluid signs of OA
Clinical and radiographic	Knee pain and at least 1 of 3	Age > 50 y Stiffness < 30 min Crepitus on active motion and osteophytes
Clinical	Knee pain and at least 3 of 5	Age > 50 y Stiffness < 30 min Crepitus on active motion Bony tenderness Bony enlargement No palpable warmth of synovium

ACR = American College of Rheumatology; OA = osteoarthritis.