BACKGROUND: The treatments of knee osteoarthritis are mainly to relieve the symptoms, and it is difficult to be cured. Exercise therapy is denominated as a designed and ruled plan of physical activities to get some specific treated goals and aimed at the recovery of normal musculoskeletal function and reduction of the pain caused by diseases or body injuries. The research of exercise therapy in prevention and treatment of knee osteoarthritis has different opinions. OBJECTIVE: To discuss the critical factors influencing exercise therapy in the prevention and treatment of knee osteoarthritis, and to provide reference for exercise therapy in preventing and treating knee osteoarthritis. METHODS: A computer-based retrieval of CNKI and PubMed databases was performed for the articles published before January 2019. The keywords were “exercise therapy, knee osteoarthritis, prevention and treatment” in Chinese and English, respectively. The articles concerning exercise therapy effect on knee osteoarthritis were included for analysis based on inclusion and exclusion criteria. RESULTS AND CONCLUSION: (1) Exercise therapy should be begun as early as possible, and at the early period, we should pay attention to the angle of knee joint injury, and increase the intensity gradually, such as from non-weight training to weight training. (2) The middle-low intensity exercise therapy is recommended, and over-training should be avoided, especially for those who have cartilage wear.