Background: High tibial osteotomy was first described in 1958 as a successful treatment for moderate to severe unicompartmental, degenerative arthritis of the knee associated with angular deformity. Malalignment is frequently associated with knee arthrosis and can influence the mechanical load through either the medial or the lateral compartment. Aim of the work: Investigation of the clinical and radiographic results of opening-wedge high tibial osteotomy and fixated by locked compression plate, when used to as surgical treatment of osteoarthritis and varus deformity. Patients and methods: The study took place at Al Azhar University Hospital {Elhussein and Bab EL Sharia}. It was a prospective study on 20 consecutive patients who had knee osteoarthritis and varus knee deformity. They were treated by surgical intervention by opening wedge high tibial osteotomy applied by T – locked plate, between September 2016 to April 2019. The procedures are carried out under spinal anesthesia. Results: There was a significant improvement in the pain level after surgery when compared to before surgery. Postoperatively, 16 patients (80%) were found to have no pain. Pre-operatively 19 patients (95%) had full range of knee motion, and only one patient had hyperextension. Post-operatively, all patients had maintained their full knee extension. Postoperatively, 60% of the patients showed normal alignment, 10% valgus (mean: 1° valgus) and 30% still varus (mean: 2.33° varus, range: 1-4°). Conclusion: The patients in this study were satisfied with the results. Younger patients planning for HTO should be advised about the benefits and risks of the procedure, specifically mentioning kneeling and scar formation.