Background: knee deformity is one of the most common presentations in pediatric orthopaedic clinic. It could be pathological or normal as a result of skeletal maturation. The gold standard for treating knee deformity is osteotomy. Normalization of the mechanical axis helps distribution of stress of body weight on all knee compartments and ligaments so prevent early development of knee osteoarthritis. Patients: It is a prospective study of 56 patients with knee deformity .genu varus having metaphyseal-diaphyseal angle greater than 11, genu valgus with a greater than 15-degree tibio-femoral angle, full extension range of motion and flexion greater than 100, exclusion of genu recuravatum, and limb length discrepancy. The patients' ages range from 10 to 18 years. Methods: Each patient assessed clinically for knee range of motion and pain as well as their radiological deformity correction and union. A nine-month follow-up period. Results: The results of patients operated by external fixation by monolateral external fixator were as follows: The deformity in all the 28 patients had been corrected. Mild pain was experienced in 16 cases (57.14%), moderate pain was experienced in 8 cases (28.57%) and severe pain was experienced in 4 cases (14.28%). The duration of union (in months) had a mean value of 2.23. Pin tract infection occurred in 14 patients (50%), 2 patient had superficial infection at the osteotomy site (8.33%) and no infection was encountered in 12 patients (41.67%). The results of patients operated by internal fixation were as follows: The duration of union in all the 28 patients was about 3.5 months. The pain score after union was mild in 14 cases (50%) and moderate in 14 cases (50%) patients. ROM of knee was >90 degree in 14 cases (50%) and >100 degree in 14 cases (50%). Wound infection occurred in 4 cases (14.29%) and no infection occurred in 24 cases (85.71%).