Ultrasonographic identification of pelvic floor myofascial trigger points and their correlation with clinical symptoms in patients with pelvic floor myofascial pain

Chronic pelvic pain (CPP) is a multifactorial pain syndrome characterized by discomfort arising from pelvic organs or related anatomical structures and persisting for more than six months. This condition is commonly associated with maladaptive cognitive responses, sexual dysfunction, and emotional distress, and may involve dysfunction of the lower urinary tract, reproductive system, gastrointestinal tract, pelvic floor myofascia, or sexual function ( 1 ). Although CPP is frequently attributed to gynecologic causes, approximately 80% of cases are not primarily of gynecologic origin ( 2 ). Pelvic floor myofascial pain (MFP) constitutes a significant subset of CPP and is frequently associated with urinary, anorectal, and sexual dysfunction. Common symptoms include dyspareunia, pelvic pressure, and pain localized to the vaginal or perineal regions ( 3 ). Reports indicate that up to 85% of patients with CPP present with symptoms attributable to MFP ( 4 ). Clinical manifestations may include vaginal pain, sensations of pelvic organ prolapse, dysuria, or symptoms resembling recurrent urinary tract infections ( 4 , 5 ). Wang et al. constructed and evaluated a diagnostic model for postpartum pelvic floor MFP based on clinical factors and multimodal ultrasound parameters using data from 346 patients, demonstrating considerable diagnostic potential ( 6 ). Although the underlying pathophysiological mechanisms of MFP remain incompletely understood, the condition is believed to result from complex interactions among immune, neurological, and endocrine dysregulation along with psychological factors. MFP frequently develops following pregnancy, childbirth, or gynecologic surgery, which may lead to injury, adhesions, or spasm of the pelvic floor muscles (PFMs) and fascia, resulting in the formation of characteristic myofascial trigger points (MTrPs) ( 7 ). The presence of MFP significantly affects treatment outcomes and overall quality of life ( 8 - 10 ). Among patients diagnosed with interstitial cystitis/bladder pain syndrome, the prevalence of MFP ranges from 50% to 90% ( 10 ). Due to the often nonspecific nature of presenting symptoms such as low back pain or vaginal pain, accurate diagnosis remains challenging. Many patients undergo multiple consultations across specialties, face diagnostic delays, and may be subjected to unnecessary surgical procedures prior to identifying the underlying condition. As MFP represents a potentially treatable cause of CPP, improved recognition and the implementation of standardized evaluation protocols are essential for improving diagnostic accuracy and patient outcomes. MTrPs are focal areas of muscle tightness and tenderness that can generate referred pain patterns. Utilizing transvaginal ultrasound was able to precisely locate MTrPs in pelvic floor muscles, which could then be correlated with specific pain symptoms reported by patients ( 3 , 11 ). This study aimed to characterize the clinical and ultrasonographic features of MTrPs within the PFMs and to analyze their correlation with specific pain symptoms. These findings support the advancement of evidence-based diagnostic approaches and the optimization of individualized management strategies for patients with MFP. We present this article in accordance with the STROBE reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1-2515/rc ).

Medical records of 110 patients with clinically suspected chronic pelvic MFP who presented at Yiwu Traditional Chinese Medicine Hospital between January 2024 and June 2025 were retrospectively reviewed. Complete clinical data were available for 70 patients, who were included in the final analysis. Inclusion criteria: (I) clinically suspected MFP; (II) female sex and age >20 years; (III) absence of underlying conditions such as hypertension, diabetes mellitus, pulmonary tuberculosis, or cardiac disease; and (IV) ability to comprehend and accurately complete the questionnaire. Exclusion criteria: (I) age <20 years; (II) presence of organic diseases including malignancy, endometriosis, ascites, or other causes of increased intra-abdominal pressure, or active urinary tract infection; (III) coexisting respiratory diseases such as chronic cough or asthma; and (IV) refusal to participate. The flow diagram was shown in the Figure 1 . The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of Yiwu Traditional Chinese Medicine Hospital (No. 2024-019). Written informed consent was obtained from all participants. Flow diagram of the study. MFP, myofascial pain. Color Doppler ultrasound systems (GE Voluson E8, GE Healthcare, Waukesha, US and Canon Aplio i900, Canon Medical Systems Corporation, Otawara, Japan) equipped with IC5-9-D and 11C3 endocavity transducers operating at 3 to 10 MHz were used for all examinations. The questionnaire collected the following data: (I) demographic characteristics, including name, age, height, weight, body mass index (BMI; calculated as weight in kilograms divided by height in meters squared), and parity; (II) relevant medical history, including previous pelvic surgery, menopausal status, dyspareunia, and anxiety; and (III) symptoms related to chronic pelvic floor MFP, including low back pain, perineal pain, vaginal pain, groin pain, inner thigh pain, dyspareunia, and dysuria. Data were collected through in-person or telephone interviews after obtaining informed consent. Pain intensity was assessed using the 11-point Numerical Rating Scale [NRS; 0–10] for chronic pain, a validated tool suitable for verbal administration ( 12 ). Scores were classified as follows: no pain [0], mild pain [1–3], moderate pain [4–6], and severe pain [7–10]. All questionnaires and ultrasound-based measurements of PFMs were verified for accuracy and completeness prior to data entry. Patients were grouped based on the presence of clinical symptoms, including low back pain, perineal pain, vaginal pain, groin pain, inner thigh pain, dyspareunia, and dysuria. Correlation analyses were conducted to assess the relationship between the severity of MFP identified by transvaginal ultrasound and corresponding clinical symptoms. In accordance with the International Continence Society recommendations, vaginal examination is essential for assessing PFM function ( 13 ). Following bladder emptying, digital vaginal palpation was conducted by an experienced gynecologist using single-finger pressure of approximately 0.4 to 0.5 kg to assess selected PFMs (puborectalis, pubococcygeus, iliococcygeus, and coccygeus) and pelvic wall muscles (piriformis and obturator internus). Trigger points and corresponding pain scores were recorded during the examination. All ultrasound assessments were conducted by senior gynecologic sonographers with more than 5 years of clinical experience in pelvic floor imaging. Transvaginal ultrasound was performed in accordance with established protocols, incorporating the clock-face orientation method and standardized digital examination techniques ( 14 - 16 ): (I) identification of the perineal body using the vaginal introitus as the reference point; (II) insertion of the transducer into the vagina to visualize the anal mucosa and internal and external anal sphincters; (III) scanning of the levator ani muscle complex, including the bilateral puborectalis, pubococcygeus, and iliococcygeus muscles; (IV) examination of the obturator internus muscle; and (V) identification of the piriformis and coccygeus muscles. Each muscle was evaluated for fiber continuity, echogenicity, and alignment. Trigger point pain severity was rated using the NRS [0–10], categorized as no pain, mild pain, moderate pain, or severe pain, with patients selecting the score corresponding to their perceived pain level. Currently, no universally accepted diagnostic gold standard has been established for pelvic MFP. Diagnosis is generally based on a comprehensive assessment that incorporates clinical symptoms, physical examination findings, and imaging results. The primary diagnostic criteria included: (I) clinical presentation: persistent pelvic pain along with identifiable trigger points in the PFMs; (II) palpation assessment: identification of trigger points through digital vaginal examination and ultrasound evaluation; and (III) imaging assessment: ultrasound-based evaluation of the anatomical structure and functional integrity of PFMs. (I) All gynecologic examinations were conducted by a single experienced gynecologist to ensure procedural consistency. (II) Ultrasound assessments were conducted by an experienced gynecologist using standardized protocols to ensure reproducibility ( 14 ). In cases involving multiple examiners, diagnostic discrepancies were resolved through consensus discussion, repeated examination, or independent expert review. (III) PFMs demonstrate homogeneous echotexture with clear muscle fiber continuity and uniform echogenicity under normal conditions. The ultrasound criteria for MTrPs were as follows: (I) location: specific anatomical landmarks within the targeted muscles (levator ani, piriformis, coccygeus, obturator internus); (II) size: localized area typically less than 1 cm in diameter; (III) echogenicity: hyperechoic or hypoechoic compared to surrounding muscle tissue; (IV) boundaries: well-defined borders separating from normal muscle tissue; (V) fiber pattern: disruption or alteration of normal muscle fiber alignment; (VI) clinical correlation: correspondence with tender points identified during digital examination. Comparative assessment of normal and abnormal findings allowed for the identification of pathological muscle changes ( 17 - 19 ). This observational study was conducted in accordance with established reporting standards for clinical research. Statistical analyses were performed as follows: (I) continuous variables, including name, age, height, weight, BMI (calculated as weight in kilograms divided by height in meters squared), and parity, were analyzed as continuous data. (II) Binary variables included history of pelvic surgery, menopausal status, dyspareunia, and anxiety (yes/no). (III) Clinical symptoms related to chronic pelvic floor MFP, such as low back pain, perineal pain, vaginal pain, groin pain, inner thigh pain, dyspareunia, and dysuria, were analyzed as binary variables (yes/no). Clinical pain reports were compared with ultrasound-derived pain scores. For continuous variables with normal distributions, independent-samples t-tests were used. Categorical variables were analyzed using chi-squared tests. Spearman rank correlation coefficients were used to evaluate variable relationships. Additional logistic regression analyses were conducted to examine the relationship between muscle pain scores and the presence/absence of symptoms, adjusting for potential confounders including age, parity, history of pelvic surgery, and anxiety status. Binary logistic regression was used to analyze the influencing factors related to clinical pain symptoms. Presence or absence of clinical symptoms was taken as the outcome variable, while age, height, weight, BMI, number of deliveries, whether pelvic surgery was performed, whether menopause occurred, whether anxiety existed, and MTrPs were regarded as independent variables. The Enter method was adopted. Based on the results of logistic regression analysis, seven prediction models for different clinical symptoms were established. The Hosmer-Lemeshow (H-L) test and generalized coefficient of determination (R 2 ) were used to evaluate the fitting effect of the models, and the prediction accuracy of the seven models was compared. A two-tailed P<0.05 was considered statistically significant.

A total of 70 patients were included in the final analysis. The mean age was 39.77±10.87 years (range, 23–74 years), mean height was 160.45±5.28 cm (range, 145–173 cm), mean weight was 56.69±7.75 kg (range, 40–83 kg), and mean BMI was 22.03±2.97 kg/m 2 (range, 16.20–31.00 kg/m 2 ). Regarding parity, 8.06% of patients were nulliparous, 62.10% had one delivery, 29.03% had two deliveries, and 1.81% had three or more deliveries. A history of pelvic surgery was reported by 47.58% of patients, 85.48% were premenopausal, and 23.39% reported symptoms of anxiety. Baseline demographic and clinical data are presented in Tables 1,2 . BMI, body mass index; SD, standard deviation. Among all participants, voiding difficulty was reported by 28 patients (40%), 21 (30%) experienced defecation difficulty, 33 (47%) presented with dyspareunia, 17 (24%) experienced perineal pain, and 3 (4.8%) reported vaginal pain. Additionally, 38 patients (54.8%) reported left-sided low back pain and 35 (50%) reported right-sided low back pain. Both left and right groin pain were reported by 4 patients each (6.4%). Left lower abdominal pain was reported by 9 patients (12.9%), middle-lower abdominal pain by 1 patient (1.6%), and right lower abdominal pain by 11 patients (15.3%). Furthermore, 38 patients (54.8%) experienced left buttock pain and 35 (50%) reported right buttock pain. The distribution of pain-related symptoms is presented in Table 3 . From clinical presentations, mean NRS scores indicated mild pain in the bilateral levator ani muscles, bilateral obturator internus muscles, and the right coccygeus muscle, while the left coccygeus muscle demonstrated moderate pain intensity. Moderate pain was also recorded in the bilateral piriformis muscles. Transvaginal ultrasound indicated that MTrPs were primarily located in the bilateral piriformis and coccygeus muscles. Detailed ultrasound findings are presented in Table 4 and Figure 2 . NRS, Numerical Rating Scale; SD, standard deviation. Two-dimensional transvaginal ultrasound of pelvic floor muscles presenting the distribution of myofascial trigger points and corresponding NRS pain scores. NRS, numerical rating scale; R-ICM 3, right iliococcygeus muscle NRS score 3; R-ICM 6, right iliococcygeus muscle NRS score 6; R-OI 0, right obturator internus muscle NRS score 0; R-OI 5, right obturator internus muscle NRS score 5; R-PM 2, right piriformis muscle NRS score 2; R-PM 7, right piriformis muscle NRS score 7. The Spearman rank correlation coefficient analysis demonstrated statistically significant associations between muscle-specific MTrPs and clinical pain symptoms (P<0.05 for all correlations unless otherwise specified). Dyspareunia was significantly correlated with MTrPs in the left piriformis muscle (ρ =0.288, P=0.013) and right obturator internus muscle (ρ =0.439, P<0.001). Vaginal pain was correlated with MTrPs in the left and right piriformis muscles (ρ =0.287 and 0.336, respectively). Left low back pain was significantly correlated with MTrPs in the left levator ani, left obturator internus, right obturator internus, left coccygeus, left piriformis, and right piriformis muscles (ρ =0.439, 0.479, 0.473, 0.322, 0.265, and 0.489, respectively). Right back pain was significantly correlated with MTrPs in the left coccygeus, Left piriformis, and right piriformis muscles (ρ =0.304, 0.572, and 0.545, respectively). Left lower abdominal pain demonstrated significant correlations with MTrPs in the left levator ani and left coccygeus muscles (ρ =0.256 and 0.254). Right lower abdominal pain demonstrated significant correlations with MTrPs in the left levator ani muscle (ρ =0.232, P=0.048). Middle-lower abdominal pain demonstrated significant correlations with MTrPs in the left levator ani, left obturator internus, right obturator internus, left coccygeus, left piriformis, right piriformis muscles (ρ =0.277, 0.337, 0.299, 0.352, 0.689, and 0.842, respectively). Given the low number of positive events, these results should be considered exploratory and require validation in larger samples. Left buttock pain demonstrated significant correlations with MTrPs in the left levator ani, left obturator internus, right obturator internus, right coccygeus, left piriformis, right piriformis muscles (ρ =0.256, 0.521, 0.795, 0.362, 0.306, and 0.332, respectively). Right buttock pain demonstrated significant correlations with MTrPs in the left levator ani, left obturator internus, right obturator internus, left coccygeus, left piriformis, right piriformis muscles (ρ =0.277, 0.337, 0.299, 0.352, 0.689, and 0.842, respectively). These findings are presented in Table 5 . FDR procedure used BenjaminiHochberg and the significance threshold (P<0.05). *, P<0.05; **, P<0.01. FDR, false discovery rate. According to the binary logistic regression analyses ( Table 6 ), constipation was correlated with age [odds ratio (OR): 1.111; 95% confidence interval (CI): 1.006–1.228; P=0.038], history of pelvic surgery (OR: 4.474; 95% CI: 1.063–18.822; P=0.041), and menopause (OR: 0.019; 95% CI: 0.001–0.508; P=0.018). Dyspareunia was associated with two deliveries (OR: 0.162; 95% CI: 0.043–0.603; P=0.018). BMI, body mass index; CI, confidence interval; OR, odds ratio. *, P<0.05; **, P<0.01.

Pelvic floor MFP resulting from MTrPs has been recognized as a major contributor to CPP in women ( 20 ). Although the underlying mechanisms of MFP remain incompletely defined, current evidence indicates that repetitive microtrauma or sustained muscle overload can induce prolonged muscle contraction and local ischemia, leading to the development of MTrPs ( 16 , 21 ). This study used a multidimensional analytic approach that integrated ultrasonographic imaging and pain scoring to comprehensively examine the correlations between pelvic floor MTrPs and clinical symptoms. The findings demonstrated that dyspareunia was significantly correlated with MTrPs in the left piriformis muscle (ρ =0.222, P=0.013), while vaginal pain was associated with MTrPs in the right coccygeus and right piriformis muscles (ρ =0.216 and 0.217, respectively; P<0.05). These results are consistent with prior reports that emphasize the key role of MTrPs in the pathophysiology of MFP ( 14 ). Additionally, left groin pain was correlated with the bilateral levator ani and left obturator internus muscles, and buttock pain on both sides demonstrated associations with the coccygeus, piriformis, and obturator internus muscles. These findings highlight distinct and reproducible patterns between pain distribution and specific muscle involvement, underscoring the diagnostic use of transvaginal ultrasound for localized assessment of pelvic floor muscle dysfunction in patients with MFP. Physical examination consistently presented palpable MTrPs within the pelvic floor muscles of patients, consistent with previously reported clinical features of MFP, including dyspareunia and lower abdominal pain ( 4 ). Ultrasonographic assessment confirmed that left buttock pain correlated with bilateral coccygeus, bilateral piriformis, and right obturator internus muscles (ρ =0.545, 0.414, 0.799, 0.440, and 0.271, respectively; P<0.05), while right buttock pain demonstrated significant correlations with the same muscle groups (ρ =0.321, 0.618, 0.192, 0.425, and 0.825, respectively; P<0.05). These findings demonstrate that transvaginal ultrasound enhances precision in identifying MTrPs, allowing for accurate localization of pain origins within the pelvic musculature. Further analysis indicated that left low back pain was correlated with MTrPs in the bilateral coccygeus, bilateral levator ani, and bilateral piriformis muscles (ρ =0.466, 0.314, 0.249, 0.201, 0.343, and 0.332, respectively; P<0.05). Comparable correlations were observed for right low back pain (ρ =0.466, 0.275, 0.179, 0.214, and 0.525, respectively; P<0.05). Additionally, left groin pain was associated with MTrPs in the bilateral levator ani and left obturator internus muscles (ρ =0.197, 0.226, and 0.184, respectively; P<0.05). These results reinforce the significant role of the levator ani muscle in the development of MFP. The levator ani is particularly susceptible to MFP syndrome ( 22 ). Levator ani syndrome contributes to chronic anal pain, although its precise pathophysiological mechanisms remain to be fully elucidated. In this study, a significant relationship was observed between levator ani pain severity and patient-reported low back pain (P<0.05). Furthermore, inner thigh pain demonstrated a strong association with right levator ani pain severity (P<0.01), consistent with findings reported by Dal et al. , supporting the link between levator ani dysfunction and pelvic floor pain ( 23 ). Piriformis syndrome, a condition frequently characterized by low back pain, buttock pain, and sciatica, may also manifest as dyspareunia, urinary dysfunction, constipation, or pain in the vulva, vagina, rectum, thighs, or buttocks ( 24 - 27 ). These clinical features indicate that pain may originate from trigger points within the pelvic or abdominal musculature. In most cases, MFP produces self-limiting pain episodes lasting from 30 seconds to several hours. A large-scale review involving 2,275 women aged 23 to 74 years who participated in a national prevention and treatment program reported that vulvar pain was the most prevalent symptom ( 28 , 29 ). Prior studies have indicated that approximately 57% of women with pelvic floor hypertonicity experience dyspareunia, likely attributable to muscle contraction, irritation of localized pain areas, tissue adhesions, or organ dysfunction ( 30 ). Therapeutic interventions aimed at promoting muscle relaxation may reduce pelvic floor hyperactivity, alleviate muscle spasms, and mitigate pain intensity. These results further indicated significant correlations between left piriformis muscle pain severity and dyspareunia (P<0.05). Left lower abdominal pain was correlated with the left coccygeus muscle (ρ =0.218, P=0.015), and right lower abdominal pain was correlated with the left levator ani and right piriformis muscles (ρ =0.211 and 0.185, respectively; P<0.05). Groin pain exhibited a marginally significant relationship with right obturator internus muscle pain intensity (P=0.047). Bilateral obturator internus muscle pain was associated with anal incontinence, loose stool, and flatulence, while right obturator internus and left levator ani muscle pain were correlated with incomplete evacuation sensation and painful defecation ( 13 , 31 ). Furthermore, right obturator internus muscle pain independently influenced subjective symptoms including pelvic floor pain, pelvic organ prolapse, lower abdominal or genital pain, incomplete rectal emptying, and pain during defecation ( 31 ). Among patients with pelvic organ dysfunction, such as urinary or defecatory disorders, impaired muscle relaxation during elimination may underlie both conditions. Common etiologies of groin pain syndrome include inguinal lesions (54.05%), acetabular labral tears (18.92%), and pelvic floor disorders (8.11%) ( 32 ). Women involved in long-term physical activity are particularly predisposed to groin pain syndrome, consistent with findings from the Italian multidisciplinary consensus ( 33 ). Existing evidence further supports the feasibility of transvaginal probe palpation for assessing pelvic floor muscle pain ( 14 , 34 ). In the present analysis, the correlation between right coccygeus muscle pain and vaginal pain did not reach statistical significance (P=0.053), indicating no definitive relationship between right coccygeus muscle pain and vaginal, perineal, or groin pain. Comprehensive assessment of pelvic organ function is therefore essential, including assessment of lower urinary tract, anorectal, sexual, gynecologic, and psychosocial factors, alongside detailed pain analysis ( 5 ). This study also distinguished between pelvic tenderness points and MTrPs. Pelvic tenderness points denote areas of generalized muscle sensitivity, while MTrPs represent discrete tender spots within taut muscle bands. MTrPs are characterized by local twitch responses and referred pain upon palpation, which can lead to restricted range of motion. Accurate identification and management of MTrPs can alleviate pain and enhance quality of life among patients with MFP. Despite the valuable findings, certain limitations should be acknowledged. First, as a cross-sectional study, causal or temporal relationships between MTrPs and symptom development could not be established. Second, the relatively small sample size may have introduced selection bias and limited the generalizability of results. Thirdly, lack of blinding may lead to measurement bias. Further randomized controlled double-blinded studies involving a larger scale and a more diverse patient population are needed to enhance the reliability and external validity of the research results. Finally, several symptoms (e.g., vaginal pain, middle-lower abdominal pain) had very few positive cases, which may lead to statistical instability in logistic regression analyses; thus, the corresponding OR and confidence intervals should be interpreted with caution.

The results of this study highlight preliminary evidence suggesting a possible relationship between MTrPs within pelvic floor and pelvic wall muscles and pain distribution in patients with MFP. By systematically correlating specific body surface pain locations with underlying muscular trigger points, ultrasonographic assessment offers a basis for individualized diagnosis and targeted therapeutic planning. Larger-scale, multicenter studies are warranted to validate these correlations and further refine diagnostic and treatment strategies for patients with MFP, thereby improving clinical outcomes and quality of life of the patients.

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