Knee Osteoarthritis Diagnosis Criteria

A subcommittee of the American College of Rheumatology developed criteria for the diagnosis of osteoarthritis affecting the knee.

Sets of criteria:

(1) clinical data only

(2) clinical, laboratory and radiographic data

Clinical data - presence of both of the following:

(1) knee pain

(2) one of the criteria in the following table

Crepitus	Morning Stiffness in the Knee	Age in Year	Bony Enlargement	Pattern
present	<= 30 minutes	>= 38 years	NA	A
present	> 30 minutes	NA	present	B
absent	NA	NA	present	C

Combined data (clinical, laboratory, radiographic) - one of the following:

(1) knee pain AND osteophytes

(2) knee pain AND one of the patterns in the table:

Synovial Fluid	Age in Years	Morning Stiffness in the Knee	Crepitus	Pattern
typical for OA	NA	<= 30 minutes	present	A
NA	>= 40	<= 30 minutes	present	B

where:

• Synovial fluid findings in osteoarthritis are clear fluid, viscous with neutrophil count < 2,000 per µL.

Performance:

• The clinical criteria have a sensitivity of 89% and specificity of 88%.

• The clinical, laboratory and radiographic criteria have a sensitivity of 94% and specificity of 88%.

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ACR Clinical Classification Criteria for Osteoarthritis of the Knee