A retrospective, age- and sex-matched radiographic study. To compare the sagittal spinopelvic alignment in patients with hip osteoarthritis (OA) stratified by stage with that of age-matched control groups. OA of the hip resulting from developmental hip dysplasia could be a cause of low back syndrome. OA of the hip may induce changes in sagittal alignment compared with healthy subjects. We studied 53 patients with OA of the hip secondary to developmental hip dysplasia, including 27 at the prearthritic/early stage (age, 34.0 years) and 26 at the advanced/terminal stage (age, 56.3 years). Comparisons were made with healthy females age-matched to each patient group (n = 13 and n = 15, respectively). Lateral roentgenograms of the lumbar spine and the hip joint were obtained in the upright position to determine pelvic inclination, sacral slope angle, lumbar lordotic angle (L1-L5), disc angle of L5/S1, and pelvic angle (by Jackson's method). Patients with pre/early-stage OA tended to have greater anterior pelvic inclination than healthy volunteers, although the difference was not significant. No significant differences were noted for other measurements. Lumbar lordotic and sacral slope angles were significantly greater in patients with advanced/terminal-stage OA than the control. Although lumbar lordotic and sacral slope angles decreased with aging in the healthy subjects, patients with OA retained the lumbar lordotic and sacral slope angles despite progression of OA with age. Pelvic inclination tended to increase in pre/early-stage OA patients. In healthy subjects, aging is associated with reduction of lumbar lordotic angle and tendency for posterior inclination of the sacrum. With aging, patients with OA maintained the lumbar lordotic angle and did not develop a posterior sacral slope angle.