In most patients with hip disorders, the anterior pelvic plane (APP) sagittal tilt does not change from supine to standing position. However, in some patients, APP sagittal tilt changes more than 10° posteriorly from supine to standing position. The purpose of this study was to both examine APP sagittal tilt and investigate the hip flexion and extension range of motion (ROM) required during daily activities in these atypical patients. Patient-specific 4-dimensional (4D) motion analysis was performed for 50 hips from 44 patients who had undergone total hip arthroplasty. All patients divided into two categories, such as atypical patients for whom the pelvis tilted more than 10° posteriorly from supine to standing position preoperatively (19 hips from 18 patients) and the remaining typical patients (31 hips from 26 patients). The required hip flexion and extension angles did not differ significantly between atypical patients and typical patients. In conclusion, the hip flexion ROM during deep bending activities and hip extension ROM during extension activities required in those atypical patients with pelvic tilt more than 10° backward from supine to standing position did not shift in the direction of extension. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:542–547, 2015.