Radiological Comparison Between Single-Leg and Double-Leg Stance in the Assessment of Genu Varum: Pre- and Postoperative Evaluation and Functional Outcomes

Overview

Genu varum, commonly known as bow-legged deformity, is characterized by an outward angulation of the knee joint that disrupts normal lower limb alignment and weight distribution(1,2). This condition alters the mechanical axis of the limb, often increasing medial compartment loading, which can accelerate degenerative joint changes and pain. Radiographic assessment plays a central role in quantifying the deformity, typically measured through parameters such as the hip-knee-ankle (HKA) angle, mechanical axis deviation (MAD), and medial proximal tibial angle (MPTA)(1,2). Weight-bearing posture during imaging significantly influences these alignment parameters. Several studies have demonstrated that single-leg stance radiographs produce more physiologically representative alignment measurements than double-leg stance, since the single-leg condition better simulates natural load distribution and joint reaction forces during locomotion(3,4). The single-leg stance increases joint compression and reveals hidden malalignments that may be masked in double-leg or non-weight-bearing positions. Consequently, preoperative evaluations based solely on double-leg stance may underestimate the severity of genu varum deformity(3,4). Surgical correction, through techniques such as high tibial osteotomy or guided growth, aims to restore the mechanical axis to a near-neutral position, improving load symmetry and delaying degenerative changes(4,5). Postoperative evaluation is essential for monitoring realignment success and predicting functional recovery, which often involves comparing radiological correction with clinical outcomes such as range of motion, pain reduction, and activity resumption. However, the correspondence between radiographic correction measured under different stance conditions and postoperative function remains poorly defined(6,7). Recent evidence suggests that patients assessed preoperatively under single-leg stance conditions may have more accurate predictions of postoperative alignment and function than those evaluated under double-leg stance (5,6). Furthermore, differences between stance types may influence surgical planning decisions, including the degree of correction targeted and the fixation technique used. Functional outcomes after genu varum correction depend not only on bony realignment but also on balanced muscular forces, proprioception, and joint stability - factors more dynamically engaged in single-leg stance evaluation(7,8). Despite increasing recognition of weight-bearing differences in radiological evaluation, limited research directly compares single-leg versus double-leg stance assessment for genu varum across preoperative and postoperative stages. Establishing which stance provides a more reliable correlation with functional outcomes could refine surgical planning, enhance rehabilitation monitoring, and standardize postoperative evaluation protocols for improved patient outcomes.