160 patients with knee osteoarthritis were randomized to receive an open-wedge high tibial osteotomy (OWHTO) (n=78) or a tibiofibular proximal osteotomy combined with an absorbable spacer (TPOASI) (n=82). The primary outcome of interest was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Secondary outcomes of interest included knee pain, radiographic parameters, Knee Society Score (KSS), operative time, blood loss, length of incision, hospital stay, and incidence of complications. Assessments were performed up to 2 years post-operation. While both procedures provided good and comparable clinical outcomes at 2 years, OWHTO significantly outperformed TPOASI in the short term, demonstrating significantly better WOMAC scores at 6 months. However, the length of hospital stay, operative time, length of incision, intraoperative blood loss, and incidence of infection were all significantly lower in the TPOASI group.