This is a narrative conceptual paper, not a systematic review. Ultrasound-guided fascial hydrorelease (FHR) has been reported to provide sustained pain relief in patients with chronic musculoskeletal pain; however, its underlying biological mechanisms remain incompletely understood. In this paper, we propose the “Fascial Memory Reset Hypothesis” as an integrative framework linking mechanobiology, extracellular matrix (ECM) remodeling, peripheral nociception, microcirculatory dynamics, and ultrasound imaging findings. Mechanobiological research has demonstrated that increased tissue stiffness activates YAP/TAZ signaling, promoting fibroblast activation, ECM deposition, and mechano-epigenetic regulation. These mechanically driven processes can stabilize pathological tissue phenotypes without DNA sequence alterations. The “Fascial Memory Reset Hypothesis” proposes that targeted mechanical interventions such as FHR may partially reverse these mechanically maintained states by restoring tissue mobility and modifying stiffness-dependent mechanotransduction. We propose that “stacking fascia” (observed as layered hyperechoic bands on ultrasound) represents the macroscopic structural phenotype of mechano-epigenetic memory formed through sustained mechanical stress. Integrating molecular mechanotransduction pathways, mechano-epigenetic mechanisms, neural sensitization, and vascular factors, we propose that FHR may hypothetically partially normalize pathological fascial states by mechanically restoring tissue mobility and modifying stiffness-dependent signaling. Although direct molecular evidence of the effect of FHR in human fascia remains limited, this hypothesis provides a biologically plausible link between mechanical stress, ultrasound-visible structural alterations, and sustained clinical improvement.

Background/Objectives: Ultrasound-guided fascial hydrorelease (FHR) occasionally elicits a brief localized contraction (“local twitch”) at the moment the needle tip contacts a fascial layer; the anatomical basis of this reaction has not yet been systematically characterized. To examine local twitch occurrence relative to stacking fascia (yes/no) at the needle tip (primary outcome), as well as the anatomical distribution and per-video capture rate (secondary outcomes). Methods: We retrospectively analyzed 11,205 ultrasound videos from a single pain clinic (October 2015–March 2026). Twitches were identified by prospective clinical observation and computational screening (frame-difference-based Profile Match classifier; 417 candidates over 30 review rounds). The stacking fascia status was independently determined by two FHR-experienced clinicians, with discordant cases jointly adjudicated. Results: Inter-rater agreement was 86/90 (95.6%; 95% CI 89.0–98.8%); one case was reassessed, deemed to not be a twitch, and excluded. In the final cohort (n = 89), local twitches occurred at stacking fascia in 89/89 (100%; 95% CI 95.9–100%). Events were concentrated in gluteal/pelvic (51%) and lumbar paraspinal (29%) regions, with a per-video capture rate of 0.98% (110/11,205; 95% CI 0.81–1.18%). Conclusions: Local twitches during ultrasound-guided FHR essentially always coincide with the needle tip lying within stacking fascia, identifying this as the structural locus within this cohort. This figure represents inclusion-criterion-bound selectivity within the twitch-positive subset, not the positive predictive value of stacking fascia for twitch occurrence.

Ultrasound-guided fascial hydrorelease (FHR) has been reported to provide sustained pain relief in patients with chronic musculoskeletal pain; however, its underlying biological mechanisms remain incompletely understood. In this review, we propose the “Fascial Memory Reset Hypothesis” as an integrative framework linking mechanobiology, extracellular matrix (ECM) remodeling, peripheral nociception, microcirculatory dynamics, and ultrasound imaging findings. Mechanobiological research has demonstrated that increased tissue stiffness activates YAP/TAZ signaling, promoting fibroblast activation, ECM deposition, and mechano-epigenetic regulation. These mechanically driven processes can stabilize pathological tissue phenotypes without DNA sequence alterations. The “Fascial Memory Reset Hypothesis” proposes that targeted mechanical interventions such as FHR may partially reverse these mechanically maintained states by restoring tissue mobility and modifying stiffness-dependent mechanotransduction. We introduce “stacking fascia” as an ultrasound-visible layered structural phenotype reflecting cumulative mechanobiological adaptation. Integrating molecular mechanotransduction pathways, mechano-epigenetic mechanisms, neural sensitization, and vascular factors, we propose that FHR may hypothetically partially normalize pathological fascial states by mechanically restoring tissue mobility and modifying stiffness-dependent signaling. Although direct molecular evidence of the effect of FHR in human fascia remains limited, this hypothesis provides a biologically plausible link between mechanical stress, ultrasound-visible structural alterations, and sustained clinical improvement.

Myofascial pain syndrome (MPS) is a major cause of chronic neck pain, with tissue ischemia implicated as a contributing factor. This prospective, single-arm interventional study evaluated the analgesic effect of ultrasound-guided fascia hydrorelease (US-FHR) performed around arteries supplying the neck in patients with chronic neck MPS. Thirteen adults (median age 53.0 years; 38.5% female) underwent US-FHR targeting the perivascular fascia of either the transverse cervical or dorsal scapular artery using 2 mL of normal saline. Pain intensity was assessed by visual analog scale (VAS) at rest and during movement; disability by the 5-item Pain Disability Index, Japanese version (PDI-5-J); and arterial blood flow volume before and after the procedure. The primary outcome, pain VAS during movement, decreased from 49.0 mm (interquartile range [IQR], 44.5–64.0) at baseline to 22.0 mm (IQR, 14.5–31.5) at 15 min and 22.0 mm (IQR, 14.0–34.0) at 1 week (Hodges-Lehmann median difference, 30.5 mm [95% CI, 24.5 to 36.5] and 28.5 mm [95% CI, 18.5 to 37.0]; both P < 0.001). Pain VAS at rest improved from 21.0 mm (IQR, 13.0–43.5) to 8.0 mm at 15 min and 1 week (median difference, 14.5 mm [95% CI, 9.0 to 24.0; P = 0.001] and 13.5 mm [95% CI, 6.0 to 21.0; P = 0.007]). PDI-5-J decreased from 17.0 (IQR, 10.5–23.0) to 13.0 (IQR, 4.0–17.5) at 1 week (median difference, 5 [95% CI, 2 to 8; P = 0.004]). Blood flow volume increased from 11.2 mL/min (IQR, 4.5–14.4) to 17.2 mL/min (IQR, 6.1–23.7) immediately after US-FHR (median difference, +4.1 mL/min [95% CI, +2.5 to +8.9; P = 0.001]), although transient. One patient experienced transient bleeding that was promptly controlled. In this single-arm feasibility study, US-FHR around the target artery was simple and safe to perform and was associated with reduced neck pain. Because the study lacked a control group, these preliminary findings should be regarded as hypothesis-generating and require confirmation in controlled trials; they may also inform the future evaluation of MPS in other anatomical regions. Trial registration: UMIN Clinical Trials Registry, UMIN000053612.

Background: Thumb pain frequently arises from multiple conditions—de Quervain’s tenosynovitis, carpometacarpal (CMC) osteoarthritis, carpal tunnel syndrome, intersection syndrome, and myofascial pain syndrome—that often coexist yet are traditionally managed as separate entities. Fascial abnormalities, including hyaluronic acid-related densification and impaired interlayer gliding, have been proposed to constitute a shared pathological substrate underlying these conditions. Ultrasound-guided fascia hydrorelease (US-FHR) targeting fascial pathology has been used clinically for thumb–wrist pain; however, the anatomical targets and treatment regions have not been systematically described. Aim: This article presents a fifteen-point US-FHR clinical protocol for five converging thumb pain conditions, based on shared fascial abnormalities—densification and impaired interlayer gliding—that these conditions may have in common. It further provides a shared practical framework for pain physicians, orthopedic specialists, hand therapists, and acupuncturists. Methods: The protocol was organized based on a focused literature review on fascial biology, thumb–wrist anatomy, and the five converging conditions, combined with long-term clinical experience at Kimura Pain Clinic. For each POINT, the anatomical rationale, associated pain pattern, procedural concept, and major safety considerations were summarized. A four-direction screening test (thumb flexion, extension, abduction, and adduction) assessed in three modes (active contraction, resistance loading, and passive stretch), combined with nine established clinical tests, was integrated to identify the affected fascial structures. A diagnostic ultrasound finding characterized by multi-layered hyperechoic bands with reduced interlayer gliding—the sonographic appearance termed “stacking fascia” (a hyperechoic, stripe-shaped lesion), a previously described morphological sign that may reflect fascial densification—is described. Results: The protocol comprises 15 POINTs distributed across two approaches: nine POINTs via a dorsal approach and six POINTs via a palmar approach. The dorsal approach (9 POINTs) covers the first and third extensor compartments, their intersections (1st–2nd and 2nd–3rd), the two radial-artery crossing points (Points 5 and 6, where the radial artery passes deep to the first-compartment and EPL/ECRB–ECRL tendons, respectively), Gokoku (Hegu), the adductor pollicis, and the deep palmar arch. The palmar approach (6 POINTs) covers the thenar muscles, transverse carpal ligament, paraneural sheath and interfascicular epineurium of the median nerve, the median-nerve/FPL/FCR interface, the median nerve within the carpal tunnel, and the deeper palmar ligamentous structures adjacent to the median nerve. Periarterial release around the radial artery is proposed as a hypothesis-generating approach to CMC osteoarthritis, in which fascial constriction of periarterial tissue may contribute to subchondral vascular compromise. For each POINT, the anatomical rationale, associated pain patterns, procedural concept, and safety considerations are integrated and described. Conclusions: The proposed fifteen-point protocol represents an expanded, structured, and clinical-experience-based framework for US-FHR in five converging thumb pain conditions sharing common fascial abnormalities. It may serve as a practical basis for the standardization, education, and broader dissemination of US-FHR in this population. Prospective observational studies, randomized controlled trials, and imaging validation studies are needed to evaluate its clinical effectiveness and to test the underlying mechanistic hypotheses, including potential periarterial vascular contributions to CMC osteoarthritis.

The local twitch response (LTR) elicited during ultrasound-guided fascial hydrorelease (FHR) is conventionally attributed to dysfunctional motor endplates. Recent observational data from a companion study suggest that LTR events may occur preferentially within stacking fascia—a histologically defined multilayered, densified region of deep fascia—at sites not directly attributable to motor endplate excitation. We propose the Fascial Capacitor Model: stacking fascia can be conceptually modeled as a multilayer biological capacitor in which collagen sublayers may act as electrodes and the interposed densified hyaluronic-acid (HA)-rich loose layer may act as the dielectric, with the LTR hypothesized to reflect a transient electrophysiological discharge when a needle bridges its layers. This biophysical model is grounded in the established molecular and histological architecture of human deep fascia, and the analogy is intended as one of structural isomorphism, rather than complete functional equivalence with engineered capacitor devices. Each premise is independently supported by the primary literature from at least eight research lines spanning roughly seventy years. The apparent gap between estimated bulk discharge voltages and motor neuron threshold is addressed by reconsidering needle-tip geometry and stimulation modality, anchored by the ±6 V triboelectric measurements. The pathological extension of the RC time constant in densified fascia—lengthening by several orders of magnitude and estimated to reach the millisecond range—is supported by empirical evidence from fibrotic extracellular matrices in other connective tissues, while tissue-specific in vivo measurements in fascia remain a future task. The model is positioned as the immediate-phase complement to the Fascial Memory Reset Hypothesis, provides a candidate mechanistic interpretation for intra-procedural symptom relief—an as-yet unquantified clinical observation awaiting formal patient-reported outcome (PRO) measurement in a prospective trial—and yields falsifiable predictions. A direct empirical validation program using insulating-needle recording of spontaneous electrical activity (SEA) is in preparation at the corresponding author’s institution.