Surgical treatment of varus unicompartmental knee osteoarthritis: indications, trends, and outcomes—a narrative review

Introduction: Varus unicompartmental knee osteoarthritis (UC-KOA) is a frequent and heterogeneous clinical condition characterized by compartment-specific cartilage degeneration and frequently associated with lower-limb malalignment. The progressive understanding of knee biomechanics and alignment has led to the development of surgical strategies specifically tailored to address isolated compartment disease. The purpose of this narrative review is to evaluate indications, current trends, and clinical outcomes of the main surgical options for varus UC-KOA, with particular focus on realignment osteotomies and unicompartmental knee arthroplasty (UKA). Materials and methods: A narrative review of the literature was conducted using major biomedical databases. Evidence related to biomechanics, alignment correction, osteotomy techniques, UKA indications, implant evolution, complication profiles, and comparative outcomes was analyzed and synthesized thematically. Results: Biomechanical and clinical evidence consistently identifies malalignment as a key driver of isolated compartment degeneration. Corrective osteotomies effectively restore physiological load distribution and provide durable outcomes in selected patients with extra-articular deformity. Advances in implant design and surgical techniques have substantially improved UKA survivorship, allowing broader patient selection without compromising clinical outcomes. Comparative studies indicate that osteotomy and UKA serve complementary roles, with specific advantages depending on patient age, activity level, deformity origin, and joint status. Conclusions: Current evidence supports an individualized, alignment-based, compartment-specific approach to the surgical management of varus UC-KOA, emphasizing patient-specific decision-making grounded in biomechanical principles.