Side-to-side weight-bearing asymmetry in subjects with low back pain

The purpose of this project was to determine if subjects with low back pain (LBP) exhibit greater side-to-side weight-bearing (WB) asymmetry compared to healthy control subjects without LBP. This study utilized an observational double cohort design and consisted of 35 subjects with LBP and 31 healthy control subjects. Side-to-side WB asymmetry was calculated as the average of the absolute value of the difference between the right and left lower extremity from three trials. The percentage of the average side-to-side WB asymmetry relative to the total body weight was calculated to normalize expected differences in magnitude of asymmetry based on a subject's total body weight. An 11-point numeric pain rating scale was used to represent the subject's current level of pain. Patients with LBP demonstrated significantly greater normalized side-to-side WB asymmetry than healthy control subjects (8.8% vs. 3.6%, respectively, P<0.001). In patients with LBP, higher magnitudes of side-to-side WB asymmetry were significantly associated with increased pain (r=0.39, P=0.021). In conclusion patients with LBP exhibited increased side-to-side WB asymmetry compared to healthy control subjects without LBP. This asymmetry was associated with increased levels of pain. This finding is relevant for planning future studies that will attempt to provide evidence for the construct validity of manipulation by determining if side-to-side WB asymmetry normalizes after a manipulation intervention and if this improvement is associated with improvements in pain and function.