Tehran University of Medical Sciences Journal of Orthopedic and Spine Trauma 2538-2330 11 1 2025 02 24 1 10 EN Roop Singh Pandit Bhagwat Dayal Sharma Postgraduate Institute of Medical Sciences, Rohtak Pradeep Kumar Positron Multispeciality Hospital, Rohtak Jitendra Wadhwani PT. B.D. SHARMA POSTGRADUATE INSTITUTE OF MEDICAL SCIENCES Svareen Kaur Baba Saheb Ambedkar Medical College, Rohini, New Delhi, India Harshil Singh Indian Institute of Information Technology, Una, India 2024 09 01 2025 02 16 Background: It is now a well-established fact that paraspinal muscle integrity plays a critical role in low back pain. We aimed  to determine the association of the cross-sectional area (CSA), muscle disc ratio (muscularity), and muscle fat ratio of the paraspinal muscles with chronic low back pain (CLBP) of varied pathologies, and  the effect of aging and BMI. Results: The CSAs of the muscles did not differ significantly between the two groups except for multifidus (p<0.05) and psoas (p<0.001) at L1-L2, and psoas (p<0.001) at L2-L3. There was significant difference in CSA of disc at L3-L4, L4-L5, L5-S1 (p<0.05), muscle fat ratio (p<0.01) and muscularity of multifidus and psoas (p<0.05) from L1 to L5 levels. There was no correlation of age and BMI with the CSA. Aging led to fatty infiltration in both the groups. The CSAs of muscles and discs were comparable (p>0.05) among subgroups except at few spinal levels. Muscularity among the subgroups varied at different levels. The muscle fat ratio were comparable (p>0.05). Conclusion:  Muscularity and composition rather than overall CSA of important spinal stabilizers  are associated with CLBP. Age and BMI has no correlation to CSA of paraspinal muscles. Various disc and muscle parameters do not differ much among common lumbar pathologies. https://jost.tums.ac.ir/index.php/jost/article/view/623 https://jost.tums.ac.ir/index.php/jost/article/download/623/395