Inclusion Criteria:  Age > 60 years Patients were diagnosed with advanced idiopathic knee OA (according to the radiological criteria of the American College of Rheumatology Guidelines) Patients who were scheduled for unilateral total knee arthroplasty in Orthopedic Clinic of University Hospital of Alexandroupolis  Exclusion Criteria:  1) Medical conditions that exercise was contraindicated (i.e cardiopulmonary comorbidities that precluded modest exercise 2) Diseases that affected their functional performance (suffering from neuromuscular or neurodegenerative conditions) 3) Mental diseases 4) Previous hip or knee joint replacement surgery 5) Severe pain on the controlateral limp that would not allow them to follow any pre- or postoperative interventions