We will study 300 people with knee osteoarthritis (OA) who receive their medical care from a large health maintenance organization (HMO) in Indianapolis. Our study will evaluate a comprehensive plan for treatment of knee OA by primary care physicians. Primary care physicians will provide standard care for knee OA to half of the study participants (150 people), and will use the comprehensive treatment plan guidelines to treat the other half. The comprehensive plan includes careful use of medications along with non-drug approaches such as patient education, exercise, and social support. People who participate in the study will receive care for knee OA for 1 year. We will measure the results (outcomes) of treatment at the start of the study and at 3 months, 6 months, and 12 months after patients join the study. The results we will measure include joint pain, physical function, drug side effects, quality of life, satisfaction with OA care, and the cost of medical care.