BACKGROUND: Percutaneous lateral hemiepiphysiodesis of the lower extremity is a simple and excellent method to correct the angular and length problems cosmetically. However, the efficacy of percutaneous lateral hemiepiphysiodesis is not well established in the literature. The purpose of this study was to evaluate the efficacy of percutaneous lateral hemiepiphysiodesis for angular corrections in adolescent idiopathic genu varum patients with proximal tibia vara and identify the factors affecting the amount of deformity correction of the lower limb in the coronal plane. METHODS: We retrospectively reviewed 20 patients (40 lower limbs) who had percutaneous lateral hemiepiphysiodesis on the proximal lateral tibia between 1997 and 2010. Radiographic evaluations were made using (1) the hip-knee-ankle angle and (2) the length of the tibia. Furthermore, the intercondylar distance was evaluated at the level of the knee joint. Preoperative factors (gender, age, body mass index, intercondylar distance, preoperative hip-knee-ankle angle, remaining growth of tibia, and calculated correctable angle) were analyzed, as well as their correlation with the degree of the actual correction angle. RESULTS: The amount of coronal deformity of the lower limb was improved from its preoperative state. The median average of hip-knee-ankle angle improved from 8.0degrees (interquartile range [IQR], 7.0degrees to 10.0degrees) preoperatively to 3.0degrees (IQR, 2.5degrees to 4.0degrees) at the final follow-up (p < 0.001). The median percent ratio of the angular correction was 60% (IQR, 50% to 71.3%). The correlation coefficients were -0.537, 0.832, 0.791, and 0.685 for the bone age, preoperative hip-knee-ankle angle, the remaining growth of tibia, and calculated correctable angle, respectively. CONCLUSIONS: Despite the excellent cosmetic outcome of percutaneous lateral hemiepiphysiodesis on the proximal lateral tibia in adolescent idiopathic genu varum, the effect was limited in most cases. For optimum results, surgery a few months earlier is recommended, rather than at the calculated operation time.