A Study of Retatrutide (LY3437943) Once Weekly in Participants Who Have Obesity or Overweight and Osteoarthritis of the Knee

Inclusion Criteria: * Have a body mass index (BMI) ≥27 kilogram/kg/m² at screening. * Have a history of at least 1 self-reported unsuccessful dietary effort to lose body weight. * Have index knee pain for \>12 weeks prior to screening, and presence of index knee pain for \>15 days over the previous month. * Have knee X-ray with moderate radiographic changes (Kellgren-Lawrence Grade 2 or 3) per central reading at screening. * Currently meets American College of Rheumatology (ACR) Criteria (clinical and radiological) for OA. Exclusion Criteria: * Have had steroid joint injections within 90 days of screening. * Have had other joint injections and procedures within 6 months of screening. * Have joint disease other than osteoarthritis. * Have a self-reported or documented change in body weight \>5 kg (11 pounds) within 90 days prior to screening. * Have been taking weight loss drugs, including over-the-counter medications, within 90 days prior to screening. * Have a prior or planned surgical treatment for obesity. * Have diabetes mellitus.