• Psychological impairment [ Time Frame: Measured immediately, 6 months, and 12 months following treatment: pain ] [ Designated as safety issue: No ]
  
• Physical disability [ Time Frame: Measured immediately, 6 months, and 12 months following treatment: pain ] [ Designated as safety issue: No ]
  
• Joint stiffness [ Time Frame: Measured immediately, 6 months, and 12 months following treatment: pain ] [ Designated as safety issue: No ]
  
• Activity level [ Time Frame: Measured immediately, 6 months, and 12 months following treatment: pain ] [ Designated as safety issue: No ]
  
• Physical activities [ Time Frame: Measured immediately, 6 months, and 12 months following treatment: pain ] [ Designated as safety issue: No ]
  

• Physiological measures of disease activity [ Time Frame: Measured immediately, 6 months, and 12 months following treatment: pain ] [ Designated as safety issue: No ]
  
• Gait measures [ Time Frame: Measured immediately, 6 months, and 12 months following treatment: pain ] [ Designated as safety issue: No ]
  

Osteoarthritis is a chronic, degenerative joint disorder that does not have a cure. While OA can occur at almost any joint, it most commonly occurs in the knee. Obesity is a significant risk factor for the development of knee OA and is associated with faster disease progression. Biomechanical inflammation and cognitive behavioral changes related to obesity can exacerbate OA pain and disability. The purpose of this study is to develop more effective ways to treat individuals with knee OA. Specifically, the study will compare the effectiveness of a lifestyle behavioral weight management program, pain-coping skills training, and standard care in improving OA symptoms and day-to-day function in obese individuals with OA in one or both knees.

The study treatment groups will meet for a total of 6 months. Participants will be randomly assigned to one of four conditions: 1) lifestyle behavioral weight management program, 2) pain-coping skills training, 3) lifestyle behavioral weight management program plus pain-coping skills training, or 4) standard care. The lifestyle behavioral weight management program will focus on lifestyle, exercise, attitudes, relationships, and nutrition. The pain-coping skills training will focus on minimizing maladaptive over-reactions and enhancing adaptive strategies to control and decrease pain. Standard care will include routine medical care.

Participants in the first three conditions will attend 12 weekly group sessions, followed by 6 every-other-week group sessions. After completing treatment, participants will receive monthly follow-up telephone calls to facilitate the post-treatment transition. There will be a total of four evaluations during this study: immediately prior to treatment, immediately after treatment, and 6 and 12 months following the end of treatment. During each evaluation, blood and urine will be collected to analyze disease biomarkers. An exercise treadmill test and height, weight, and body mass index measures will be used to assess aerobic fitness. Lower extremity function will be measured with the "Up and Go" performance test. Participants will also be videotaped while walking to evaluate gait and will be asked to fill out a series of questionnaires. Medication use will be reviewed during an interview. During the first evaluation, x-rays will be taken to measure disease activity.

Participants completing the study intervention and all four follow-up evaluations will be eligible to join the second part of the study examining the relationship between food intake, mood, activity level, and pain. Participants will complete a series of questionnaires at baseline and 2-day diaries in which they rate mood, pain, and activity level and they record food intake triggered at random times throughout the day. A follow-up visit to complete additional questionnaires will be conducted 6 months later. Blood samples will also be collected for future analysis of genetic markers of pain sensitivity.