High tibial osteotomy is effective for managing a variety of knee conditions, including gonarthrosis with varus or valgus malalignment, osteochondritis dissecans, osteonecrosis, posterolateral instability, and chondral resurfacing. The fundamental goals of the procedure are to unload diseased articular surfaces and to correct angular deformity at the tibiofemoral articulation. Although the clinical success of total knee arthroplasty has resulted in fewer high tibial osteotomies being done during the past decade, the procedure remains useful in appropriately selected patients with unicompartmental knee disease. Renewed interest in high tibial osteotomy has occurred for a number of reasons. These include the prevalence of physiologically young active patients presenting with medial compartment osteoarthritis; the advent of new techniques for performing the procedure (ie, improved instrumentation and fixation plates for medial opening wedge osteotomy, dynamic external fixation for medial opening wedge osteotomy, and improved instrumentation for lateral closing wedge osteotomy); and the need to concomitantly correct malalignment when performing chondral resurfacing procedures (ie, autologous chondrocyte transplantation, mosaicplasty, and microfracture).