This meta-analysis and systematic review included 193 studies (84 randomized controlled trials were assessed in the meta-analysis) comparing physical therapy to a control group in patients with knee osteoarthritis (OA). The most effective interventions were ultrasonography, and aerobic, aquatic, strengthening, and proprioception exercise. Education, orthotics, taping, tai chi, and pulsed electromagnetic fields had no clinically significant effect on any of the patient-centered or functional outcomes of interest. Few adverse events occurred in the studies.