OA is the most common form of arthritis in the United States. Symptoms of knee OA include pain in and around the knee that typically worsens with weight-bearing activities, morning stiffness, and tenderness. A person with OA who experiences a torn meniscus--a cartilage structure within the knee that provides stability and proper weight distribution--is especially at risk for disability. Past studies have shown that arthroscopic partial meniscectomy (APM), a type of knee surgery, usually relieves symptoms and improves function in people suffering from a meniscal tear. However, the success of APM is more variable among people with already existing OA. Clinicians are also uncertain about the short- and long-term benefits, drawbacks, and indications for APM in people with OA and meniscal tears. The purpose of this study is to compare the effectiveness of two treatments, APM surgery and standard physical therapy, for people with OA and a torn meniscus.