Iran University of Medical Sciences , shabnamshahali@yahoo.com
Abstract: (58 Views)
Background & Aims: The utilization of ultrasound imaging has continued to expand, primarily due to its distinct advantages over other diagnostic modalities. These benefits include its cost-effectiveness, portability, and non-invasive nature, allowing clinicians to acquire real-time imaging data across a broad spectrum of patient populations.
The application of ultrasound imaging in rehabilitation, referred to as rehabilitative ultrasound imaging, originated with its use in evaluating tissue morphology rather than detecting pathological abnormalities (1). The technique was developed in the 1980s and continued to evolve in the following decades, culminating in the inaugural International Symposium on rehabilitative ultrasound imaging, held in 2006 in San Antonio, Texas (2, 3). The second symposium occurred in Madrid in 2016, and its findings demonstrated an expanded application of ultrasound in physiotherapy (4). In recent years, the application of ultrasound imaging in physiotherapy has grown significantly. Notable uses of ultrasound in this field include rehabilitative ultrasound imaging (such as the assessment of muscle morphology and function, biofeedback, etc.) (2, 6), diagnostic ultrasound imaging (for evaluating muscle injuries, etc.) (2, 7), interventional ultrasound imaging (e.g., dry needling), and research ultrasound imaging (8). Beyond its established applications in musculoskeletal and sports physiotherapy (3, 9), ultrasound imaging is increasingly being utilized in emerging areas such as pelvic floor health in both women (10-12) and men (13), cardiorespiratory physiotherapy (14), pediatric care (15, 16), and neurological physiotherapy (17, 18).
The growing use of ultrasound imaging in physiotherapy necessitates a deeper understanding of its various applications. Gaining a clearer insight into the global landscape of ultrasound use by physiotherapists will offer valuable knowledge to inform the development of educational guidelines, curriculum standards, and evidence-based physiotherapy protocols for the application of ultrasound imaging. The primary focus of this narrative review was the application of ultrasound imaging in neuro-musculoskeletal assessments performed by physiotherapists.
Methods: A comprehensive search of PubMed, Scopus, Google Scholar, Cochrane Library, and Web of Science databases was conducted from inception to June 2025. The review included studies that investigated the use of ultrasound imaging for neuromusculoskeletal assessment conducted by physiotherapists.
Results: Ultrasound imaging has been shown to have acceptable reliability and validity for evaluating muscle morphometry. Previous studies have demonstrated acceptable levels of reliability for intra-rater, inter-rater, same-day, and between-day measurements (34–36). The reliability of ultrasound imaging has been established across various muscle groups, including those of the spine (37, 38), trunk (15, 39, 40), pelvis (41, 42), and extremities (33, 43), and different populations. To evaluate the validity of ultrasound imaging, its results have been compared with those obtained from established reference standards. Magnetic resonance imaging (MRI) is commonly used as the standard reference for assessing muscle morphology, while electromyography serves as the standard reference for evaluating muscle function (6). Research has demonstrated that ultrasound imaging possesses acceptable validity for assessing muscle activity of the trunk and lumbar spine during most isometric and submaximal contractions (45, 47). The significance of ultrasound imaging in rehabilitation lies in its capacity to assess muscle groups during contraction. This capability is particularly crucial for analyzing motor control and muscle activation patterns in deep muscles that are challenging to evaluate through non-invasive methods. Recent studies have increasingly employed ultrasound imaging to quantify changes in muscle thickness, serving as an indirect measure of muscle activity (12, 45, 47, 51). Compared to fine-wire electromyography, ultrasound imaging is a noninvasive technique suitable for clinical application. Moreover, it enables the visualization of a broader region of the muscle than can be assessed with intramuscular electrodes (21, 52, 53). However, it is noteworthy that the majority of these studies have evaluated validity under resting or static conditions. Since assessing muscle parameters using ultrasound imaging during dynamic tasks presents greater challenges, further research is warranted to establish its validity in such contexts. It is also important to note that changes in muscle thickness, as measured by ultrasound imaging, are influenced by multiple factors, with muscle activity being only one of them. Variables such as the resting state of the muscle, the structural and mechanical properties of the muscle-tendon unit, the type of contraction (isometric, concentric, eccentric), and the presence of external forces (such as fascial attachments, intra-abdominal pressure, or adjacent muscle activity) can all affect ultrasound measurements. Additionally, methodological factors related to the imaging technique may impact the changes in muscle thickness during contraction. To control these factors, researchers implement certain precautions during imaging. For instance, when assessing trunk muscles, it is critical to avoid imaging during activities that induce substantial increases in intra-abdominal pressure, such as coughing, sneezing, or limb movements. Additionally, it is essential to maintain a consistent position, orientation, and internal pressure of the ultrasound probe throughout the imaging process. Any deviation from these parameters may lead to probe movement relative to the body, resulting in inaccurate interpretations of muscle function (10).
Several modes are available to visualize the electrical signals generated by returning ultrasound echoes from tissues. In rehabilitative settings, the most commonly employed display modes are B-mode (brightness), M-mode (motion), and elastography (7). The most frequent application of ultrasound imaging in studies conducted by physiotherapists was the assessment of muscle structural properties using B-mode. This typically includes measuring parameters such as muscle thickness, width, and cross-sectional area, and comparing these measurements across different groups, time points, or conditions, such as before and after an injury or therapeutic intervention (e.g., exercise) (7, 10, 12, 48, 49). B-mode ultrasound imaging captures data along the full length of the probe, enabling researchers to assess the effects of different positions and motor tasks on anatomical structures within the imaging field (10). The relatively wide field of view offered by B-mode ultrasound imaging, combined with the real-time capabilities, provides the opportunity to simultaneously visualize multiple anatomical structures and monitor them dynamically over time (7).
M-mode ultrasound imaging allows researchers to measure changes in muscle thickness over time. In contrast to B-mode, which generates a cross-sectional image of an anatomical region using data acquired along the entire length of the probe, M-mode displays information obtained from the probe’s midpoint (10). In M-mode ultrasound imaging, fixed structures appear as straight lines, whereas moving structures generate wave-like patterns, allowing for the measurement of movement frequency and direction. This mode has been used by physiotherapists to assess the onset of muscle activity. Comparisons between M-mode ultrasound and electromyography indicate that M-mode offers accuracy comparable to electromyography, though it records muscle activation with a slight temporal delay (27–29).
Elastography offers a direct, noninvasive method for quantifying the stiffness of soft tissues such as muscle, tendon, and ligament. This mode is particularly valuable for monitoring transient or progressive muscle changes associated with neurological disorders. Additionally, elastography has demonstrated utility in evaluating muscle responses to clinical interventions aimed at reducing stiffness and spasticity in neurological conditions. Emerging evidence suggests that elastography techniques hold clinical potential for assessing the effectiveness of physiotherapeutic interventions targeting musculoskeletal stiffness (30, 31).
Ultrasound imaging is also utilized in physiotherapy as a biofeedback tool to facilitate the rehabilitation of pelvic floor muscles and lateral abdominal wall muscles, particularly in patients with urinary incontinence, low back pain, and pelvic girdle pain (42, 54, 55).
Additionally, ultrasound imaging has been utilized to safely guide the insertion of dry needles for various interventions, including acupuncture (61), trigger point release (62), and percutaneous electrolysis—an approach that involves delivering mechanical stimulation and electrical current through an acupuncture needle to induce controlled microtrauma and facilitate tissue repair (63).
Conclusion: The findings of this narrative review indicate that ultrasound imaging demonstrates acceptable validity and reliability for the assessment of muscle morphological properties. Although changes in muscle thickness are influenced by muscle activity, they result from a combination of several factors, including the muscle's resting state, extensibility, flexibility, tendon structure, type of contraction, image interpretation variables, and aspects of the ultrasound imaging technique. Consequently, changes in muscle thickness observed via ultrasound imaging should not be used as a surrogate measure of muscle activity without accounting for these confounding variables. Ultrasound imaging also serves as a valuable biofeedback tool. Therefore, it is recommended that future research focuses on enhancing the methodological quality, assessing cost-effectiveness, and clinical efficacy of ultrasound imaging in the physiotherapy management of neuro-musculoskeletal conditions.
Conflicts of interest: None
Funding: None
The application of ultrasound imaging in rehabilitation, referred to as rehabilitative ultrasound imaging, originated with its use in evaluating tissue morphology rather than detecting pathological abnormalities (1). The technique was developed in the 1980s and continued to evolve in the following decades, culminating in the inaugural International Symposium on rehabilitative ultrasound imaging, held in 2006 in San Antonio, Texas (2, 3). The second symposium occurred in Madrid in 2016, and its findings demonstrated an expanded application of ultrasound in physiotherapy (4). In recent years, the application of ultrasound imaging in physiotherapy has grown significantly. Notable uses of ultrasound in this field include rehabilitative ultrasound imaging (such as the assessment of muscle morphology and function, biofeedback, etc.) (2, 6), diagnostic ultrasound imaging (for evaluating muscle injuries, etc.) (2, 7), interventional ultrasound imaging (e.g., dry needling), and research ultrasound imaging (8). Beyond its established applications in musculoskeletal and sports physiotherapy (3, 9), ultrasound imaging is increasingly being utilized in emerging areas such as pelvic floor health in both women (10-12) and men (13), cardiorespiratory physiotherapy (14), pediatric care (15, 16), and neurological physiotherapy (17, 18).
The growing use of ultrasound imaging in physiotherapy necessitates a deeper understanding of its various applications. Gaining a clearer insight into the global landscape of ultrasound use by physiotherapists will offer valuable knowledge to inform the development of educational guidelines, curriculum standards, and evidence-based physiotherapy protocols for the application of ultrasound imaging. The primary focus of this narrative review was the application of ultrasound imaging in neuro-musculoskeletal assessments performed by physiotherapists.
Methods: A comprehensive search of PubMed, Scopus, Google Scholar, Cochrane Library, and Web of Science databases was conducted from inception to June 2025. The review included studies that investigated the use of ultrasound imaging for neuromusculoskeletal assessment conducted by physiotherapists.
Results: Ultrasound imaging has been shown to have acceptable reliability and validity for evaluating muscle morphometry. Previous studies have demonstrated acceptable levels of reliability for intra-rater, inter-rater, same-day, and between-day measurements (34–36). The reliability of ultrasound imaging has been established across various muscle groups, including those of the spine (37, 38), trunk (15, 39, 40), pelvis (41, 42), and extremities (33, 43), and different populations. To evaluate the validity of ultrasound imaging, its results have been compared with those obtained from established reference standards. Magnetic resonance imaging (MRI) is commonly used as the standard reference for assessing muscle morphology, while electromyography serves as the standard reference for evaluating muscle function (6). Research has demonstrated that ultrasound imaging possesses acceptable validity for assessing muscle activity of the trunk and lumbar spine during most isometric and submaximal contractions (45, 47). The significance of ultrasound imaging in rehabilitation lies in its capacity to assess muscle groups during contraction. This capability is particularly crucial for analyzing motor control and muscle activation patterns in deep muscles that are challenging to evaluate through non-invasive methods. Recent studies have increasingly employed ultrasound imaging to quantify changes in muscle thickness, serving as an indirect measure of muscle activity (12, 45, 47, 51). Compared to fine-wire electromyography, ultrasound imaging is a noninvasive technique suitable for clinical application. Moreover, it enables the visualization of a broader region of the muscle than can be assessed with intramuscular electrodes (21, 52, 53). However, it is noteworthy that the majority of these studies have evaluated validity under resting or static conditions. Since assessing muscle parameters using ultrasound imaging during dynamic tasks presents greater challenges, further research is warranted to establish its validity in such contexts. It is also important to note that changes in muscle thickness, as measured by ultrasound imaging, are influenced by multiple factors, with muscle activity being only one of them. Variables such as the resting state of the muscle, the structural and mechanical properties of the muscle-tendon unit, the type of contraction (isometric, concentric, eccentric), and the presence of external forces (such as fascial attachments, intra-abdominal pressure, or adjacent muscle activity) can all affect ultrasound measurements. Additionally, methodological factors related to the imaging technique may impact the changes in muscle thickness during contraction. To control these factors, researchers implement certain precautions during imaging. For instance, when assessing trunk muscles, it is critical to avoid imaging during activities that induce substantial increases in intra-abdominal pressure, such as coughing, sneezing, or limb movements. Additionally, it is essential to maintain a consistent position, orientation, and internal pressure of the ultrasound probe throughout the imaging process. Any deviation from these parameters may lead to probe movement relative to the body, resulting in inaccurate interpretations of muscle function (10).
Several modes are available to visualize the electrical signals generated by returning ultrasound echoes from tissues. In rehabilitative settings, the most commonly employed display modes are B-mode (brightness), M-mode (motion), and elastography (7). The most frequent application of ultrasound imaging in studies conducted by physiotherapists was the assessment of muscle structural properties using B-mode. This typically includes measuring parameters such as muscle thickness, width, and cross-sectional area, and comparing these measurements across different groups, time points, or conditions, such as before and after an injury or therapeutic intervention (e.g., exercise) (7, 10, 12, 48, 49). B-mode ultrasound imaging captures data along the full length of the probe, enabling researchers to assess the effects of different positions and motor tasks on anatomical structures within the imaging field (10). The relatively wide field of view offered by B-mode ultrasound imaging, combined with the real-time capabilities, provides the opportunity to simultaneously visualize multiple anatomical structures and monitor them dynamically over time (7).
M-mode ultrasound imaging allows researchers to measure changes in muscle thickness over time. In contrast to B-mode, which generates a cross-sectional image of an anatomical region using data acquired along the entire length of the probe, M-mode displays information obtained from the probe’s midpoint (10). In M-mode ultrasound imaging, fixed structures appear as straight lines, whereas moving structures generate wave-like patterns, allowing for the measurement of movement frequency and direction. This mode has been used by physiotherapists to assess the onset of muscle activity. Comparisons between M-mode ultrasound and electromyography indicate that M-mode offers accuracy comparable to electromyography, though it records muscle activation with a slight temporal delay (27–29).
Elastography offers a direct, noninvasive method for quantifying the stiffness of soft tissues such as muscle, tendon, and ligament. This mode is particularly valuable for monitoring transient or progressive muscle changes associated with neurological disorders. Additionally, elastography has demonstrated utility in evaluating muscle responses to clinical interventions aimed at reducing stiffness and spasticity in neurological conditions. Emerging evidence suggests that elastography techniques hold clinical potential for assessing the effectiveness of physiotherapeutic interventions targeting musculoskeletal stiffness (30, 31).
Ultrasound imaging is also utilized in physiotherapy as a biofeedback tool to facilitate the rehabilitation of pelvic floor muscles and lateral abdominal wall muscles, particularly in patients with urinary incontinence, low back pain, and pelvic girdle pain (42, 54, 55).
Additionally, ultrasound imaging has been utilized to safely guide the insertion of dry needles for various interventions, including acupuncture (61), trigger point release (62), and percutaneous electrolysis—an approach that involves delivering mechanical stimulation and electrical current through an acupuncture needle to induce controlled microtrauma and facilitate tissue repair (63).
Conclusion: The findings of this narrative review indicate that ultrasound imaging demonstrates acceptable validity and reliability for the assessment of muscle morphological properties. Although changes in muscle thickness are influenced by muscle activity, they result from a combination of several factors, including the muscle's resting state, extensibility, flexibility, tendon structure, type of contraction, image interpretation variables, and aspects of the ultrasound imaging technique. Consequently, changes in muscle thickness observed via ultrasound imaging should not be used as a surrogate measure of muscle activity without accounting for these confounding variables. Ultrasound imaging also serves as a valuable biofeedback tool. Therefore, it is recommended that future research focuses on enhancing the methodological quality, assessing cost-effectiveness, and clinical efficacy of ultrasound imaging in the physiotherapy management of neuro-musculoskeletal conditions.
Conflicts of interest: None
Funding: None
Type of Study: review article |
Subject:
Physiotherapy
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