Background: Abnormal posture creates abnormal stress and strain in many spinal structures which are considered predisposing factors for chronic mechanical low back pain.

Purpose: To examine the relationships among pain intensity, forward head posture (decreased craniovertebral angle) and lumbopelvic sagittal alignment (pelvic incidence, pelvic tilt, sacral slope, and lumbar lordosis) in chronic mechanical low back pain patients.

Methods: A cross-section correlational study was conducted on one hundred patients. A numerical-pain-rating scale was used to determine pain intensity. Standardized standing lateral radiographs were analyzed to measure the spinopelvic angles. Reported data were analyzed using correlation coefficients, and regression analyses.

Results: Lumbar lordosis had very strong positive correlations with each pain intensity and sacral slope. Pain intensity had a strong positive correlation with sacral slope. Moderate positive correlations highlighted between pelvic tilt and craniovertebral angle. Moreover, the pelvic incidence had weak positive correlations with each sacral slope and pelvic tilt. Negative correlations were strong between pelvic tilt and each of pain intensity, lumbar lordosis and sacral slope. Craniovertebral angle had moderate negative correlations with each of pain, lumbar lordosis, and sacral slope. However, the pelvic incidence had no relations with pain, craniovertebral angle lumbar lordosis. Overall, an association of demographic data and measured variables had a significant effect on the pain multi-regression equation prediction model. They accounted for 76.60% of the variation in pain.

Conclusion: Abnormal spinopelvic posture relates to chronic mechanical low back pain. There are significant associations among pain intensity, FHP and lumbopelvic sagittal alignment in chronic mechanical low back pain patients.