Abstract Osteoarthritis (OA) is a leading cause of musculoskeletal pain and disability. According to a study by Lawrence et al, an estimated 27 million Americans were living with OA in 2008. This number will continue to increase as the population of persons older than 65 years grows. Because of the increasing number of persons who have this chronic condition that causes pain and decreases function, the prevalence of this diagnosis in primary care and musculoskeletal clinics likely will increase. The reduction of pain and improvement in function should be goals of providers who treat these patients. Physical therapy (PT) is a commonly used treatment modality for persons with OA. Many treatment modalities are available within the scope of PT, including strength training, manual therapy, aquatic therapy, electrical stimulation, and balance and perturbation training. A review of the most recent and highest-quality literature regarding these modalities found that strength training, aquatic therapy, and balance and perturbation therapy were the most beneficial with respect to reducing pain and improving function. Evidence clearly indicates that electrical stimulation likely has very little impact on these variables, and evidence regarding manual therapy is equivocal. Literature reviewing prognostic indicators for persons with OA who will likely respond to PT reveal that persons with milder disease (ie, unilateral OA, symptoms for less than 1 year, and a 40-m self-paced walking test of less than 25.9 seconds) and those who have pain of 6 or greater on the numerical pain rating scale are likely to have better outcomes with PT, which suggests that earlier referral is preferable. Barriers to the acceptance of PT as a therapeutic treatment for OA include fatalistic patient and provider perspectives, inadequate analgesia, and a fear among some patients and providers that increased activity will lead to progression of their OA.