MRI demonstrates psoas and rectus atrophy plus lower trunk and hip strength in chronic low back pain compared with healthy controls.
Study Design and Imaging Approach
Chronic low back pain remains a leading driver of disability, yet the contribution of muscle morphology and strength imbalance is still being clarified. In this case control study, investigators compared trunk and hip muscle cross sectional area on lumbosacral magnetic resonance imaging with isokinetic strength measures in 50 patients with chronic low back pain and 30 healthy controls.
Magnetic resonance imaging was used to quantify cross sectional area across key paravertebral muscles, including the psoas major, quadratus lumborum, erector spinae, and multifidus, alongside rectus abdominis and selected hip muscles, including the iliacus and gluteus maximus. Strength testing assessed trunk and hip flexor and extensor performance, with analyses supported by effect size estimates and correlation testing.
Chronic Low Back Pain and Selective Muscle Differences
Patients with chronic low back pain showed smaller psoas major cross-sectional area at L2 and L5, as well as smaller rectus abdominis cross sectional area at S2 and S3, compared with controls. In contrast, there were no group differences in quadratus lumborum, erector spinae, multifidus, iliacus, or gluteus maximus morphology.
Functionally, trunk flexor and trunk extensor strength were lower in the chronic low back pain group. The trunk flexor to trunk extensor ratio was also reduced, indicating a relative shift in strength balance. Hip flexor to hip extensor ratios suggested a trend toward imbalance, including a modest difference on the left side.
Morphology Strength Links and Clinical Relevance
Correlations between cross sectional area and strength were stronger in patients with chronic low back pain, most notably for the psoas major. The authors interpret this pattern as consistent with selective morphological change that may amplify functional asymmetry. Together, the findings connect chronic low back pain with targeted atrophy of specific trunk muscles and measurable strength deficits that could contribute to ongoing impairment.
Reference: Ivanac D et al. MRI-Based Assessment of Trunk and Hip Muscle Morphology and Strength in Chronic Low Back Pain. Med Sci Monit. 2026;32:e951651.
