Knee osteoarthritis (OA) is often associated with pain, functional impairment and various degrees of disability. Physiotherapy in combination with both aerobic and strength training exercises have shown positive effects in both the pre-operative and post-operative period. At the initial stages of osteoarthritis, physical therapy and education can improve the functional outcome and the participation of patients in daily activities. In the case of OA progression and when an operation is the only effective treatment, physiotherapy is very useful in enhancing self-esteem and minimising depression and anxiety for the forthcoming surgery. Post-operative intense physical therapy and Continuous Passive Motion (CPM) application offer remarkable benefits in terms of faster recovery, shorter hospital stay and increase of range of motion. Furthermore, home-based excercises following discharge from the hospital should be encouraged in order to optimise the final result. Although the entire mechanism remains unclear, physical exercise protocols may be beneficial for patients and the health system alike.