Objective: We aimed to assess the effect of 6 mm lateral-wedge insole on both pain and function in women with clinically and radiologically documented knee osteoarthritis (OA) compared to patients using no insole. Materials and Methods: Thirty seven women with unilateral knee pain, who were diagnosed with knee OA grade II and III according to the radiographic criteria of Kellegren Lawrence grading system, were included in the study. The patients randomized into either treated with exercise and analgesic plus 6 mm wedge insole (19 patients) or only with analgesics and exercise (18 patients). Pain while walking, standing and at rest was recorded on a 100 mm Visual Analogue Scale (VAS), pain with passive motion was evaluated by Doyle’s Ritchie Index, and functional status was evaluated by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at baseline, 1st month and 3rd month visits. Results: At the 3rd month visit, the ratio of patients with improvement according to the Ritchie Index score was higher in the group using 6 mm wedge insole compared to group using no insole (p=0.008). The patients using 6 mm wedge insole had significant improvement in WOMAC pain subscale (p=0.003) and total WOMAC (p=0.01) scores at the 1st month visit and VAS at rest (p=0.03), standing (p=0.02), walking (p=0.01), total WOMAC (p=0.001), and all subscales of WOMAC (except WOMAC stiffness score) at the 3rd month visit compared to group using no insole. Conclusion: 6 mm lateral wedge insole significantly reduces pain while walking, standing, at rest and with passive movement of the knee in patients with grade II and III knee osteoarthritis. At the end of the 3rd month, besides pain reduction, significant improvement in function was observed in patients using wedge insole compared to patients treated only with analgesics and exercises.