AssessmentofMyofascialTriggerPointsviaImaging:ASystematicReview

Myofascial pain syndrome (MPS) affects up to 85–95% of patients with chronic musculoskeletal pain, yet diagnosis relies primarily on manual palpation, which has poor inter-rater reliability. Myofascial trigger points (MTrPs) are hypersensitive nodules in taut muscle bands, classified as active (spontaneous pain) or latent (pain only with stimulation). Because physical examination is subjective and unreliable, researchers have pursued objective imaging biomarkers to improve diagnosis and track treatment response. This systematic review addresses the critical need to evaluate whether imaging techniques can reliably characterize MTrPs and MPS.

The authors systematically searched PubMed, Embase, Ovid MEDLINE, Cochrane Library, and Scopus for peer-reviewed studies published between 2000–2021 that used imaging to quantitatively characterize MTrPs or MPS. After screening 1,762 abstracts and reviewing 69 full-text articles, 33 studies met inclusion criteria. Imaging modalities included ultrasound (US) with various techniques (B-mode, vibration sonoelastography, shear-wave elastography, compression sonoelastography, Doppler, texture analysis), magnetic resonance imaging (MRI) including magnetic resonance elastography (MRE), and infrared thermography. The authors extracted data on study methodologies, populations, sample sizes, and MTrP properties measured.

Methodological quality was assessed using the QUADAS tool for 13 studies that distinguished between clinically relevant groups.

Ultrasound was the most frequently used modality (23 studies). Sonoelastography studies consistently showed MTrPs as stiffer than adjacent muscle tissue, with elastic modulus values of 12.3–14.7 kPa in MTrPs versus 5.0–8.0 kPa in adjacent muscle. Shear-wave speeds in MPS patients ranged 2.0–5.0 m/s, significantly higher than controls. Texture analysis achieved promising diagnostic accuracy: Kumbhare et al. reported 95.6% sensitivity and 97.3% specificity for classifying healthy versus MPS participants; Behr et al. reported 88% sensitivity and 86% specificity.

Doppler US revealed altered blood flow at MTrPs, including higher prevalence of retrograde flow and increased pulsatility index at active versus normal sites. MRI studies showed MTrPs as focal signal alterations on T2 mapping, with 15 of 16 clinically identified MTrPs successfully identified; MRE found taut band stiffness of 10.9–11.5 kPa but poor agreement (63%) with clinical evaluation. Thermography yielded contradictory results for detecting MTrPs, with some studies finding increased temperatures (0.8–1.5°C) and others finding no difference. Only two thermography studies reported diagnostic test accuracy: 62.5% sensitivity and 71.3% specificity.

Treatment effects on stiffness were mixed: three studies found decreased stiffness after dry needling or high-power US, while three found no change after ischemic compression, dry needling, or acupuncture. MTrP area measurements varied widely across studies (3.40–5.35 mm² to 0.48–0.49 cm²). QUADAS assessment of 13 studies showed generally sound methodological quality, with participant spectrum and time interval between examination and imaging as main concerns.

This review establishes that MTrPs are objectively real, measurable phenomena—specifically, localized areas of increased muscle stiffness with altered blood flow—validating decades of clinical observations. For clinicians, this means imaging can potentially supplement unreliable palpation, with US-based methods currently the most viable option due to cost, availability, and ease of use. Sonoelastography and Doppler US show particular promise for distinguishing active MTrPs from latent ones and from healthy tissue. However, significant barriers remain before routine clinical adoption: study methodologies are highly heterogeneous, precluding standardized diagnostic thresholds; most studies were small and exploratory rather than rigorous diagnostic accuracy trials; and the reference standard (Travell and Simons' criteria) itself is imperfect.

Patients with chronic myofascial pain may benefit from more objective, reproducible diagnosis in the future, especially if imaging can predict treatment response or track outcomes. The review calls for future research to prioritize reproducibility studies, larger clinical trials with consecutive sampling, and development of consistent quantitative measures across platforms. Molecular imaging with PET radioligands targeting specific biochemical markers represents a promising but distant frontier.