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.