Knee varus deformity is a condition where the mechanical axis of the lower extremity is displaced medially. As a result, the medial compartment of the knee is overloaded and is prone to degenerative changes. The mechanical compromise of the medial compartment of the knee is very disabling, especially if affecting young and active individuals. Valgus-producing high tibial osteotomies (HTOs) were designed to shift the mechanical axis laterally, transferring the load to the knee compartment which is asymptomatic. HTO is a well-accepted concept for the management of medial unicompartmental knee arthritis. Medial joint line pain associated with metaphyseal varus deformity in a young patient is the essential criteria to indicate an HTO. Symptomatic young patients who do not have a bone-on-bone pathology may be benefited from HTO since for those individuals a unicompartmental knee replacement is contraindicated. Surgical technique matters in cases of HTO. Dome, lateral closing wedge, and medial opening wedge techniques have been reported with mixed results. Recent developments in fixation techniques, namely, the development of implants with angular stability, introduced safety, and reproducibility to open wedge HTOs, which became the preferred correction method for varus deformity of the knee. This article aims to cover the indications and contraindications of HTO with a focus on the unique aspects of the biplanar open wedge tibial osteotomy.