The relationship between spino-pelvic parameters with coronal lower extremity alignment in patients with low back pain: a prospective radiographic study.

PURPOSE: Spine-pelvic parameters and lower limb alignment serve as key clinical indicators in orthopedics. It remains unclear whether these measures are interrelated. This study examines the relationship between spine-pelvic parameters and coronal lower extremity alignment in individuals with low back pain (LBP). METHODS: We prospectively enrolled LBP patients aged over 50 years from April 1, 2023 to September 30, 2025. Radiographic evaluation included standing full-spine lateral and posteroanterior views, along with lower extremity posteroanterior radiographs. Spine-pelvic parameters assessed were pelvic incidence (PI), lumbar lordosis, pelvic tilt, sacral slope, sagittal vertical axis, and coronal balance distance. Lower extremity parameters included the hip-knee-ankle angle (HKA) and Kellgren-Lawrence grade. Parameters were compared across groups, and correlation analyses were conducted. RESULTS: The study included 264 patients (mean age 64.1±7.3 years; 63.6% female). Mean PI was 49.8±10.5°, and mean HKA was 177.2±4.1°. Significant differences in HKA were observed among PI groups (P=0.002), and PI differed significantly across HKA groups (P=0.026). A weak negative correlation was found between PI and HKA (r=-0.183, P=0.003). Sacral height showed significant correlations with PI (P<0.001) and HKA (P=0.010). CONCLUSIONS: A weak inverse association exists between PI and HKA in LBP patients, and sacral height was found to have significant influences on PI and HKA.