Paraspinal Muscle Fatty Infiltration as a Predictor of Intervertebral Disc Degeneration and Pain Severity in Chronic Low Back Pain

Background Chronic low back pain (CLBP) is commonly associated with paraspinal muscle fatty infiltration and intervertebral disc degeneration (IDD); however, their independent contributions to pain and disability, as well as the influence of Body Mass Index (BMI) on these associations, remain unclear. Objective This study aimed to investigate the associations of paraspinal muscle fatty infiltration rate (FIR) and cross‐sectional area (CSA)—specifically of the multifidus (MF), erector spinae (ES), and psoas major (PM)—with IDD severity, clinical metrics (pain (Visual Analog Scale [VAS]) and disability (Oswestry Disability Index [ODI])), and demographic factors (age, sex, and BMI) in patients with CLBP. Methods A cross‐sectional study included 118 CLBP patients. FIR and CSA of paraspinal muscles at L2–S1 were quantitatively measured on MRI using ImageJ. IDD was graded using the Pfirrmann system. Correlations and group comparisons were statistically analyzed. Results FIR showed significant sex‐based differences but no left–right asymmetry and was not associated with BMI. MF FIR was strongly positively correlated with Pfirrmann grade ( r > 0.7, p < 0.05). FIR of MF and ES was positively correlated with age and disease duration, as well as VAS and ODI scores ( r > 0.6, p < 0.05), whereas CSA showed only weak correlations. The PM exhibited minimal associations with clinical or degenerative parameters. Conclusion Paraspinal muscle fatty infiltration, especially in the MF and ES, is strongly associated with IDD severity, pain, and disability independently of BMI. FIR could serve as a potential imaging biomarker for assessing CLBP severity and progression.