Masseter muscle thickness, jaw functional limitation, oral behaviors, and psychosocial factors in chronic non-specific neck pain: A cross-sectional study.

Background: Chronic non-specific neck pain (CNSNP) and temporomandibular disorders are frequently comorbid disorders.

Objective: To evaluate masseter muscle thickness (MMT) via ultrasonography in women with/without CNSNP and compare oral behaviors, jaw function, and psychosocial factors.

Methods: This cross-sectional study enrolled 30 female CNSNP patients (March-April 2025, secondary care clinic) and 30 healthy controls. Self-reported clenching/grinding was recorded. Assessments included the Neck Disability Index (NDI), ultrasonographic MMT at rest/maximum contraction, and jaw opening (painless, unassisted, assisted). Jaw function (JFLS-20), anxiety-related symptoms (GAD-7), depression-related symptoms (PHQ-9), somatization (PHQ-15), and oral behaviors (OBC) were assessed. Group comparisons used t-test, Mann-Whitney U, or χ²; correlations used Pearson's or Spearman's tests.

Results: MMT was significantly greater in the CNSNP group at rest and contraction (p < 0.05). At rest, the mean difference was -0.09 cm (95 % CI: -0.19 to -0.01, p = 0.038); at contraction, -0.12 cm (95 % CI: -0.21 to -0.02, p = 0.017). Jaw opening did not differ between groups. CNSNP patients had higher GAD-7 (p = 0.001), PHQ-9 (p = 0.002), PHQ-15 (p < 0.001), and OBC (p = 0.002) scores. MMT at contraction correlated with pain duration (r = 0.358, p = 0.005), NDI (r = 0.280, p = 0.031), JFLS-20 (r = 0.261, p = 0.044), and GAD-7 (r = 0.261, p = 0.044); resting MMT correlated with PHQ-9 (r = 0.271, p = 0.036).

Conclusion: Women with CNSNP had greater MMT and reported higher anxiety, depression, somatization symptoms, and oral behaviors. Alongside MMT evaluation, psychosocial factors appear important in this population.