Introduction: Medial Compartment Osteoarthritis of the knee is becoming a widespread problem. The surgical options include high tibial osteotomy, unicompartmental knee replacement, and total knee replacement. Replacement surgeries are not advised in the younger age group, so in these patients, high tibial osteotomy is the only option. In this study, we have assessed the functional and radiological outcomes of high tibial osteotomy done by hemicallostasis method. Method: We report the outcome of 30 patients (30 knees) who underwent hemicallostasis with a dynamic external fixator for medial compartment osteoarthritis of the knee. The radiological assessment was done with the help of Hip Knee Ankle angle. The functional scoring was done via Oxford knee score, IKDC, KOOS, and WOMAC score. Results: At a mean follow up of 35 months, the preoperatively mean HKA angle was 172 ± 30. The mean HKA angle postoperatively was 184 ± 10. Appropriate correction of the HKA angle was achieved in 24 of 30 patients (80%). Whereas, there was under correction in 3 patients (10%) and overcorrection in 3 (10%) patients. All the functional scores showed significant improvement in the postoperative scores. There was a positive correlation between the HKA angle and oxford, IKDC, KOOS, and WOMAC Score. Complications like superficial pin tract infection were seen in 3 (10%) patients, deep infection in 1 (3%), and early union of osteotomy in 1 (3%) patient leading to revision of the osteotomy. . Conclusion: HTO is effective in improving pain, function, activity of daily living, and quality of life in patients suffering from medial compartment Osteoarthritis of the knee. Hip Knee Ankle Angle is an important parameter to restore for better functional outcomes. The Advantage of using a dynamic axial fixator is the precision in achieving calculated correction without any implant in the bone once the correction is achieved along with good healing rates.