Active trigger points are common but not universal with tension-type headache: Pain features rather than musculoskeletal function may explain why

BACKGROUND: Active trigger points (ATrPs) are common and considered a peripheral nociceptive source in tension-type headache (TTH). Understanding differences in features between individuals with TTH who have few or more ATrPs is needed. OBJECTIVES: i) To determine sub-groups by the number of ATrPs present in TTH; ii) to compare headache and participant characteristics, psychological and behavioural features, number of painful areas, quantitative sensory testing (QST), tenderness scores, cervical musculoskeletal function and symptoms on cervical testing between subgroups. METHODS: This secondary analysis of a cross-sectional study involved 80 participants with TTH. Participants were assessed with multiple cervical musculoskeletal tests, pressure and cold pain thresholds, wind-up ratio, pericranial tenderness and ATrPs. RESULTS: Two clusters were formed. Cluster 1 (n = 48) with few or nil ATrPs (median 2, range 0-5) and Cluster 2 (n = 32) with multiple ATrPs (median 8, range 5-13). Individuals in Cluster 2 reported a longer headache history (p = 0.026, r = 0.25), more reporting neck pain (p = 0.012, Phi = 0.30), more painful body areas (p = 0.001, d = 0.82), higher tenderness scores (all p < 0.001, all d > 1.00) and more pain on cervical musculoskeletal testing (p < 0.001 to p = 0.036, Phi = 0.18-0.85). They had less cervical joint dysfunction (p = 0.044, w = 0.24) but no differences in psychological and behavioural features and QST. CONCLUSIONS: Few features differentiated individuals with multiple ATrPs from those with only a few ATrPs. ATPs were not related to musculoskeletal function but possibly an element of pain hypersensitivity. Further research is needed to better understand ATrPs in TTH.