This prospective cohort study compared opening wedge high tibial osteotomy with use of the Puddu plate and the Vitoss synthetic cancellous bone versus closing wedge high tibial osteotomy with use of the AO/ASIF L-plate, focusing on complications (nonunions, infections, loss of correction, reoperations) and patient satisfaction (visual linear analog scale). During a 10-month period, we performed high tibial osteotomy for 40 patients experiencing medial knee osteoarthritis and a varus deformity. The average follow-up was 11 months. The complication rate in patients treated with the opening wedge technique was significantly higher regarding tibial nonunion, loss of correction, and material failure. Patients in the closing wedge group were more satisfied with the postoperative result. This study found that the Puddu plate, despite 6 weeks of nonweight bearing facilitating the osseous consolidation with Vitoss cement, was not able to maintain the correction during the time required for bone healing. [J Knee Surg. 2008;21:68-74.]