Proximal tibial osteotomy is effective for managing a variety of knee conditions, including unicompartmental arthritis with varus or valgus malalignment, instability, and chondral protection. With unicompartmental degeneration in the knee, an altered limb alignment redistributes more load to the diseased compartment, which may accelerate the degenerative process and cause severe pain. Thus, the goal of proximal tibial osteotomy is to unload the diseased articular surfaces by correcting the angular deformity at the knee. The decision to perform a proximal tibial osteotomy versus arthroplasty depends on the patient's age, activity level, and distribution of disease. The ideal candidate for this procedure is physiologically young and active with high functional demand. This article describes the surgical technique for a valgus-producing proximal tibial osteotomy to unload the medial compartment of the varus-malaligned knee.