High (proximal) tibial osteotomy has been considered as a successful and effective treatment for unicompartmental knee osteoarthritis. The main goals of this procedure are to relieve the pain, to protect the knee motion and activity, and to delay the need for a total knee arthroplasty surgery. The relatively young and active patients who have good knee mobility and stability, are always proper indication for the high tibial osteotomy. Surgeons make decision between two techniques-open or closed wedge-based on personal preference, degree of varus alignment, additional biomechanical abnormality such as ligament laxity and patella baja.