Inclusion Criteria:

• Study participants must be treated for chronic knee pain by a primary care physician at a participating HMO and satisfy American College of Rheumatology Clinical Criteria for the diagnosis of knee OA.
• All subjects will be able to read and write English, have a telephone, and give informed consent.

Exclusion Criteria:

• Significant hematologic, renal, hepatic, or cardiovascular disease (but not including mild/moderate hypertension) or any other serious medical condition that might preclude the subject's ability to participate fully in the project, keep clinic appointments, etc.
• Conditions other than knee OA which limit lower extremity function and mobility and/or would confound the evaluation of knee pain and function (e.g., clinically significant spinal or hip arthritis, painful or dysfunctional feet, peripheral vascular disease, lumbar radiculopathy, stroke, etc.).
• A known "secondary" cause of OA, including acute or chronic infectious arthritis; crystal-induced arthritis; systemic inflammatory connective tissue disease (e.g., rheumatoid arthritis, systemic lupus erythematosus); osteonecrosis; Paget's disease; or metabolic diseases, such as hemochromatosis, Wilson's disease, or ochronosis.