Morphological and Functional Changes of Core Muscles in Postpartum Women With Low Back Pain Based on Musculoskeletal Ultrasound.

Introduction: Postpartum low back pain (PLBP) is a prevalent condition linked to core muscle dysfunction. This study aimed to evaluate morphological and functional changes in core muscles using musculoskeletal ultrasound and explore their association with PLBP in postpartum women.

Materials and methods: A retrospective cross-sectional study included 105 women (35 PLBP group, 35 postpartum non-PLBP group, and 35 non-pregnant without LBP group). We assessed pain intensity and functional impairment, measured multifidus and abdominal muscle thickness by ultrasound, and assessed core stability using a unilateral hip bridge test.

Results: The PLBP group showed significantly reduced multifidus muscle thickness (resting and maximum contraction) versus both control groups (p < 0.05), though contraction capacity only differed from non-pregnant controls (p < 0.05). Abdominal muscles (internal oblique, upper rectus abdominis, transversus abdominis) exhibited significantly decreased thickness and relaxation capacity compared to non-pregnant controls (p < 0.05), but not versus postpartum non-PLBP group (p > 0.05). Core stability was significantly lower in the PLBP group than in both controls (p < 0.05), while waist circumference was larger than in non-pregnant controls only (p < 0.05). Logistic regression confirmed reduced core stability (p < 0.05) and increased waist circumference as independent PLBP risk factors.

Discussion: Core muscle atrophy and functional impairment are critical pathological mechanisms underlying PLBP, necessitating targeted interventions.