Several high tibial osteotomy (HTO) surgical techniques for the treatment of medial osteoarthritis of the varus knee have been reported. Their main objectives are the achievement of the precise correction that is necessary for the lower limb mechanical axis realignment and the alleviation of the medial joint space. Early or late recurrence of the varus deformity must be avoided and various methods of fixation have been proposed to obtain this. We present a method of single level oblique HTO with no bone removal and with blade plate fixation for the treatment of medial osteoarthritis of the knee. One hundred seventeen patients (136 knees) were operated using this technique during a 12.2-year period. In 4.5 years follow-up there were 73.8% satisfactory results while in 8.4 years follow-up there were 61.1% satisfactory results. There were 11 complications: five patients with deep vein thrombosis, four with superficial wound infection and two with temporary peroneal nerve dysfunction. This study presents the operative technique in details, evaluates the results and assesses the advantages and disadvantages of the method in relation to other techniques described in the literature.