Effects of somatic dysfunction on leg length and weight bearing.

CONTEXT Somatic dysfunctions of the pelvis, sacrum, and lumbar spine are common. Their association with leg length discrepancies has been observed; however, it is unclear which dysfunctions lead to mild changes in leg length or weight bearing distribution in asymptomatic individuals. OBJECTIVES To determine which somatic dysfunctions of the pelvic, sacral, and lumbar spine lead to minor leg length discrepancies and weight-bearing differences and to determine which of these dysfunctions are most common in the asymptomatic population. METHODS Asymptomatic participants between the ages of 18 and 40 years without a recent history of trauma were enrolled. Participants were measured from the anterior superior iliac spine to the medial malleolus; only those with mild leg length discrepancies (less than a quarter inch) were included. Weight-bearing distribution through each lower extremity was measured on a quadruped scale. Participants were then evaluated for somatic dysfunctions of the pelvis, sacrum, and lower lumbar spine. RESULTS Ninety-eight participants completed the study. The most common somatic dysfunctions were superior innominate shears, left-on-left sacral torsions, and right rotated lower lumbar spine segments. Several statistically significant associations were found. Most participants with right anterior innominate dysfunctions exhibited an ipsilateral longer leg and a contralateral shorter leg when measured in the supine position (P=.05). Participants with a left superior shear tended to exhibit a shorter left leg in the supine position (P=.05). For sacral somatic dysfunctions, participants with a left-on-left sacral torsion tended to exhibit a shorter left leg while standing (P=.02). In addition, a statistically significant association was found between right anterior innominate rotation dysfunctions and weight-bearing differences (P=.02). A greater percentage of patients with a right anterior innominate dysfunction bore more weight through their left lower extremity (45%). CONCLUSION Specific pelvic and sacral somatic dysfunctions have the potential to influence leg lengths, leading to mild disparities in length and in weight-bearing distribution through the lower extremities. (ClinicalTrials.gov number NCT01097109).