Pelvic floor muscle tenderness on digital palpation among women: convergent validity with central sensitization

BACKGROUND: Tenderness on palpation of the pelvic floor muscles (PFMs) is a clinical assessment tool used alongside other tests to identify PFM involvement in pelvic complaints including pelvic pain. Although reliability of PFM tenderness has been determined, validity has yet to be established. OBJECTIVES: To assess convergent validity of PFM tenderness on digital palpation with the presence of central pain mechanism, as determined by a score of greater than 40 on the Central Sensitization Inventory (CSI). A secondary objective was to assess the agreement between PFM tenderness and self-reported symptoms of PFM sensitivity. METHODS: Participants completed a battery of self-report questions, the CSI, and various physical assessments (blinded assessors). Convergent validity was assessed between tenderness on palpation and the CSI. Kappa statistics were used to determine agreement between tenderness on palpation and self-reported perineal pain, urinary urgency, dyspareunia, and dysmenorrhea. RESULTS: Ninety-nine female participants with hip or back pain and at least one self-reported symptom of pelvic floor dysfunction were included in the study (mean age 40.56±12.72 years). Convergent validity was found between PFM tenderness on palpation and scores greater than 40 on the CSI (X₁²=4.2,p=0.04). There was poor agreement between tenderness on palpation with dyspareunia (agreement 62.83%, Kappa=0.27), dysmenorrhea (agreement 55.75%, Kappa=0.14), or perineal pain (agreement 53.04%, Kappa=0.10). CONCLUSIONS: PFM tenderness on digital palpation confirmed convergent validity with CSI scores, suggesting central pain mechanisms. Clinicians may need to consider the role of central pain mechanisms in their clinical decision making when treating PFM dysfunction.