Study aim: The purpose of this study will be to investigate whether a 3-months (36-sessions) selected exercises program (strength, aerobic, mobility, neuromuscular, balance and breathing exercises) combined with 3 sessions pain neuroscience education (PNE) provides greater pain relief and improvement in physical performances and psychological factors in compared PNE and exercise alone, during at 6 months follow-up and whether “booster sessions” in follow-up periods may improve outcomes and increase adherence in a population of patients with knee osteoarthritis. Design: Clinical trial with control group, with four arm factorial groups, one-way blind, randomized, on 129 patients. Block design and with help site will be used for randomization. Settings and conduct: This study will be performed in the Tehran, Rheumatology Research Center of Shariati Hospital on people with knee osteoarthritis. Data evaluators and analyzers will be blind to the participants in each group. Participants/Inclusion and exclusion criteria: Inclusion: Men and women (age 40 years or older) with knee osteoarthritis (Kellgren and Lawrence grade 1 to 3 on the 1-4 scale) Exclusion: Severe osteoporosis and Patellofemoral osteoarthritis Intervention groups: 1. Selected exercises using booster sessions (36 sessions) 2. Pain neuroscience education (PNE) (three sessions of PNE given over 2 weeks) 3. PNE+ Selected exercises using booster sessions (exercise three times a week for 3-months combined with three sessions of PNE) 4. Control (educations program comprised of the self-management, an anatomy and physiology (except PNE), daily activities ergonomic, and encouragement to be active) Main outcome variables: Primary Outcomes: pain and WOMAC/ Secondary outcomes: psychological factors; physical function; muscles strength؛ Active range of motion؛ risk of fall؛ quality of life; and the exercise adherence.