Aim. To assess the efficacy of combined medical and surgical management in obtaining normal lower limb mechanical alignment in a patient cohort with genotypically similar hypophosphataemic rickets. Methods. A notes and radiograph audit was performed of all patients attending our institution with hypophosphataemic rickets: a subset with PHEX gene anomalies was studied further. Lower limb radiographs were assessed at two points during childhood and note made of treatment start, compliance; indication, timing and result of surgery. Standing leg alignment radiographs were measured at skeletal maturity or at latest review. Results. 35 patients (16 females, 18 skeletally mature) were identified. 10 commenced treatment at <12m. 11 patients (5 female) underwent 24 surgical procedures (13 for varus deformities). Surgery was bilateral in 10/11 patients. 5/14 osteotomies were performed after skeletal maturity. Malalignment was common: with NSA (neck-shaft angle) abnormalities in 20%, abnormal angles at distal femur and proximal tibia in 58% and 60% respectively and ankle abnormalities in 24%, prior to surgery. Surgical management led to normal mechanical alignment at skeletal maturity. At latest review, no patient had a leg length difference. 40% of non-operated, skeletally immature limbs have significant malalignment despite medical therapy. There was no statistical relationship between treatment onset and need for surgical correction. The relationship between non-compliance with medical treatment and surgical intervention was confounded by the changing emphasis on preferred method of surgical correction from osteotomy to guided growth. Conclusion. Even when medical treatment is commenced promptly and adhered to, significant lower limb malalignment can occur requiring surgical correction. Guided growth principles allow early deformity correction. Significance. Lower limb malalignment should not be considered a failure of medical treatment but more a consequence of the disease process. Earlier surgical intervention may encourage a more normal pattern of growth