Women with persistent pelvic pain may have increased pelvic floor muscle (PFM) tone.[1] Increased PFM tone is closely related to sexual dysfunction and impaired voiding or defecation, which may have a negative impact on women’s quality of life.[2, 3] Although the presence of increased PFM tone has been frequently described in women with persistent pelvic pain, the strength or nature of this association is unclear. Therefore, this systematic review aimed to evaluate the association between pelvic pain and increased PFM tone in women with persistent pelvic pain.

This was a systematic review with meta-analysis. The review followed PRISMA guidelines and was pre-registered on Prospero.
Six electronic databases (MEDLINE, Embase, Emcare, CINAHL, PsycINFO, and Scopus) were searched from inception to June 2021 using standardised terms. Studies that reported measures of pelvic pain and PFM tone among women over 18 years were included. All study designs were included except for case reports as well as systematic and narrative literature reviews. Studies were excluded if participants were women with neurological conditions or who had received any medications that could affect muscle tone. Studies were entered into Covidence and screened by title, abstract and full paper as necessary. Two reviewers screened titles and abstracts independently and reached agreements on articles that did not meet the inclusion criteria; the two reviewers then also independently reviewed the full text against the selection criteria.

The risk of bias of included studies was assessed using the National Heart, Lung and Blood Institute (NHLBI) Quality Assessment Tools for Observational Cohort and Cross-Sectional Studies by two reviewers. The association between pelvic pain and PFM tone was assessed using Pearson, Spearman’s correlation, or odds ratio (OR). Included studies were analysed according to how PFM tone was assessed (i.e., digital palpation, electromyography, dynamometry, manometry, ultrasound imaging, strain elastography, and myotonometry) and data were pooled using a random effects model. Effect sizes calculated from correlation coefficients were classified as: small (r ≥ 0.1), medium (≥ 0.3), and large (≥ 0.5). Heterogeneity between studies was assessed using the I2 statistic.

The electronic database search identified 1604 potentially relevant articles. Twenty-three studies met the inclusion criteria, from which 16 studies were included in the meta-analysis. The majority of included studies were cross-sectional in design. The mean score from the risk of bias assessment was 8, ranging from 5/10 to 10/10. Pelvic pain was assessed using either patient-reported outcome measures or clinician-reported outcome measures. Pelvic floor muscle tone was assessed using seven different assessment methods. 

There was a significant association between the presence of pelvic pain and increased PFM tone assessed by digital palpation (OR 8.72; 95% confidence interval [CI] 2.73, 27.89). Pelvic pain was inversely associated with PFM flexibility when evaluated using dynamometry (r = -0.29; 95% CI - 0.42, -0.17). However, there were no significant linear associations between pelvic pain and PFM tone measured by other assessment methods including electromyography, myotonometry, pressure manometry, ultrasound imaging, and strain elastography.

Pelvic pain and increased PFM tone may coexist in women with persistent pelvic pain but may not necessarily be linearly associated with each other. The association between pelvic pain and increased PFM tone could be mediated by other biopsychosocial factors that we have not necessarily captured in this systematic review and meta-analysis.

This review and meta-analysis found some evidence of the association between pelvic pain and PFM tone measured by digital palpation and dynamometry. However, we did not find linear associations between pelvic pain and PFM tone measured by other assessment methods. To better understand the nature of the association between pelvic pain and PFM tone, further research is required using valid and reliable assessment methods to quantify PFM tone while accounting for other factors that could affect the pain experience, such as variations between persistent pelvic pain conditions and the impact of a range of biopsychosocial factors on pelvic pain.

Loving, S., et al., Pelvic floor muscle dysfunctions are prevalent in female chronic pelvic pain: a cross-sectional population-based study. European journal of pain, 2014. 18(9): p. 1259-1270.
Padoa, A., et al., “The Overactive Pelvic Floor (OPF) and Sexual Dysfunction” Part 1: Pathophysiology of OPF and Its Impact on the Sexual Response. Sexual Medicine Reviews, 2020. 9(1): p. 64-75.
Faubion, S.S., L.T. Shuster, and A.E. Bharucha, Recognition and management of nonrelaxing pelvic floor dysfunction. Mayo Clinic Proceedings, 2012. 87(2): p. 187-193.

Continence 2S2 (2022) 100448
DOI: 10.1016/j.cont.2022.100448