The proposed study is a multi-center, randomized, double blind (patient and assessor), sham controlled clinical trial using a parallel 2 group design recruiting 220 patients of at least 18 years of age. The investigators will include patients presenting with clinically and radiologically diagnosed knee OA according to the criteria of the American College of Rheumatology, who experienced knee pain lasting for at least six months, and were diagnosed with radiographic severity of ≥ 2 on the Kellgren-Lawrence grading system or had one or more of the following signs and symptoms in the knee; restricted range of motion, pain in motion, crepitations, morning stiffness. Patients will be randomly allocated to receive TENS or sham TENS for 3 weeks.