Background:Osteoarthritis is the major cause of osteoarticular disability in elderly population. Knee is the most commonly affected joint and replacement surgeries are main modality of treatment in advance cases. Whereas in unicompartmental disease especially in relatively younger age group joint preserving surgeries are preferred. The aim of present study was to evaluate functional outcome of graduated open wedge high tibial osteotomy in patients with osteoarthritis of knee with less than 65 years of age.Methods:High Tibial Osteotomy through medial open wedge technique was done in 48 patients (52 knees) and stabilized by Limb Reconstruction System. Distraction was started at 7th day at the rate of 1 mm/day and continued till proper alignment was achieved. The clinical outcome of patients has been calculated on the basis of anatomical correction and functional improvement. Anatomical correction was determined on the basis of a radiological criterion (HKA angle) on scanogram. Whereas, the functional outcomes of the patients were measured on Oxford knee score (OKS) and WOMAC score scales.Result: The valgus correction in varus knees of patients were achieved by gain in mean HKA angle (increase by 11 ± 0.90). The desired range of correction in HKA angle was seen at the final follow up of 41 out of 52 knees (78.8%). There was under correction in 4 knees (7.7%) and overcorrection in 7 (13.4%) knees. All the functional scores showed significant improvement in the postoperative scores. There was a positive correlation between the HKA angle with OKS and WOMAC Score. Most common complication was superficial pin tract infection, which was seen in 7 (13.4%) patients.Conclusion:High Tibial Osteotomy by unilateral external fixator produces good clinical outcome and also has its added benefits. It is less invasive, no internal hardware present and safer in terms of neurovascular complications.