Objective: The purpose of this study was to evaluate the clinical outcome after open wedge high tibial osteotomy (OWHTO) with osteochondral autologous transplantation for spontaneous osteonecrosis of the knee. Methods: Between 2009 and 2012, seven knees in seven patients who underwent OWHTO with osteochondral autologous transplantation, were enrolled in this study. Inclusion criteria involved patients who had persistent pain due to spontaneous osteonecrosis of the medial femoral condyle. There were two women and five men with a mean age of 61 years at the time surgery. All patients were evaluated by clinical, radiological, and arthroscopic examinations preoperatively and over 1 year postoperatively. Statistical evaluation was performed using the Student’s paired t-test. The significance level was set at p=0.05. Results: All the patients achieved radiographic union at the osteotomy site and underwent the second surgery for removal of the fixation plate. The mean Japan Orthopaedic Association score