The association between static pelvic asymmetry and low back pain.

STUDY DESIGN: A cross-sectional case-control approach was used to estimate the association between low back pain of less than 12 months' duration and pelvic asymmetry among 21-50-year-old patients seeking physical therapy services. OBJECTIVE: To evaluate the premise that asymmetrical positioning of the innominates of the pelvis is a source of low back pain. SUMMARY OF BACKGROUND DATA: No published studies have been conducted to evaluate systematically the association between low back pain and pelvic asymmetry in a clinic-based sample. METHODS: Pelvic landmark data were obtained in 144 cases and 138 control subjects. The associations of low back pain with levels of pelvic asymmetry were estimated by use of odds ratios and 95% confidence intervals. Effect modification and confounding of the low back pain-pelvic asymmetry association by several factors was assessed and alternative asymmetry measures considered. RESULTS: Pelvic asymmetry was not positively associated with low back pain in any way that seemed clinically meaningful. Asymmetry of posterior superior iliac spine landmarks showed some evidence of a weak positive association with low back pain. CONCLUSIONS: In the absence of meaningful positive association between pelvic asymmetry and low back pain, evaluation and treatment strategies based on this premise should be questioned.