Modified Ashworth Scale

Issues of Concern

Spasticity has traditionally been measured using the MAS. Despite its popularity, the MAS is not without its critics. Although the MAS has been studied extensively for reliability, findings have been inconsistent. The inter-rater reliability of the scale has been reported to vary significantly depending on the muscle group being assessed, the examiner's experience, and methodological inconsistencies in applying the scale. The MAS demonstrated relatively high inter-rater agreement for certain muscle groups, such as the elbow flexors, but lower reliability in others, such as the lower limb musculature.[8][9][8] Other investigations have questioned whether differences in ratings reflect true variations in spasticity or discrepancies in examiner technique.[7]

Although the MAS is a widely used method for assessing spasticity, it has been criticized for its inability to differentiate between the many factors that can contribute toward resistance to passive stretch. Other methods, including the Modified Tardieu Scale, Wartenberg Pendulum Test, Clinical Gait Analysis, Penn Spasm Frequency Scale, Visual Analog Scale, and Spinal Cord Assessment Tool for Spasticity, have been proposed and used, but each has its own limitations. In 2012, Numanoglu et al conducted a study assessing spasticity in 37 children with cerebral palsy and found that the MAS demonstrated low-average intraobserver reliability, whereas the Modified Tardieu Scale showed average-excellent intraobserver interobserver reliability.[10]

Furthermore, the MAS includes the additional grade of 1+, which attempts to provide a finer gradation of spasticity severity. However, this categorization has been criticized for lacking clear differentiation between 1 and 1+, leading to ambiguity and reducing the ordinal consistency of the scale.[7]

Although the MAS is a useful tool for measuring spasticity, it may not be entirely reliable from a psychometric standpoint. Given the advancements in rehabilitation science, familiarity among spinal cord injury clinicians may not be a good enough reason to continue using this assessment tool. Validity should not be sacrificed at the expense of familiarity. Validity is a concern with the MAS, as the scale primarily quantifies resistance to passive movement rather than isolating spasticity. As initially defined by Lance, spasticity is a velocity-dependent increase in muscle tone due to the hyperexcitability of the stretch reflex. However, resistance to passive movement is influenced by multiple factors beyond spasticity, which can complicate assessment accuracy. Muscle stiffness and contracture contribute to increased resistance due to soft tissue changes, although these are not directly linked to neural hyperexcitability. Joint abnormalities, such as structural limitations in range of motion, may further obscure the true extent of spasticity. In addition, patient positioning and examiner technique play a critical role, as variations in limb stabilization or movement can influence the perceived level of resistance.

Because of these confounding factors, the MAS is often regarded as a measure of muscle tone rather than a specific measure of spasticity. A 2025 review by Gal et al explicitly excluded Ashworth-derived scales from its recommendations for assessing spasticity, emphasizing that they do not align with contemporary definitions of spasticity.[11] 

Another critical limitation of the MAS is its reduced sensitivity to detecting changes in spasticity over time. The scale uses a 0–4 grading system that does not allow for fine distinctions in incremental changes, making it difficult to assess treatment effects, particularly for subtle improvements.[12] For instance, studies evaluating the responsiveness of MAS to pharmacological interventions or rehabilitative therapies have found only modest correlations between changes in MAS scores and actual functional improvements.

Instrumented measures, such as surface electromyography, biomechanical assessments, and neurophysiological tools, have been proposed as more reliable alternatives for quantifying spasticity. These measures can distinguish between neural and mechanical components of resistance.[13] However, such approaches remain largely confined to research settings.

The lack of standardization in administering the MAS poses challenges to its reliability. Key factors contributing to variability include the speed of passive movement—as spasticity is velocity-dependent—yet no strict guideline exists on the optimal speed for limb manipulation. Examiner training and experience also play a crucial role, with more experienced clinicians demonstrating greater intra-rater reliability compared to those with limited exposure to the MAS. In addition, patient positioning affects muscle tone and perceived resistance, leading to inconsistencies in scoring. 

Given the limitations of the MAS, other assessment tools have been explored. The Tardieu Scale has been suggested as a superior alternative due to its ability to differentiate spasticity from contracture by assessing resistance at different velocities.[11] Similarly, the Composite Spasticity Index and instrumented assessments using electromyography and dynamometry offer more precise and quantitative means of measuring spasticity.[13]

Clinical Significance

Spasticity affects a broad range of patients following an inciting event. Recent scientific research has shown that spasticity occurs in 20% to 30% of post-stroke patients.[14] In a recent study, clinicians examined the prevalence of increased muscle tone, including typical spasticity and contracture, 7 years after a stroke. One-third of patients with ischemic stroke before 70 years showed increased muscle tone at a 7-year follow-up.[15] Post-stroke spasticity is one of many conditions that can lead to pain, impairment, disability, or handicap. Due to its clinical simplicity, the MAS can be used in clinical practice to benefit these patients by measuring the efficacy of both pharmaceutical and rehabilitation therapies.[15] The MAS is a muscle tone assessment scale used to assess the resistance experienced during the passive range of motion, which does not require any instrumentation and is quick to perform.[16] The MAS is the current standard for clinical assessment of extremity spasticity and is the most commonly used tool to evaluate the efficacy of pharmacological and rehabilitation interventions for the treatment and management of spasticity in patients with spinal cord injury.[16][14] The MAS serves as the gold standard for validating new assessment tools.

The MAS holds significant clinical value as the most widely used spasticity assessment tool in practice. The prevalence of MAS can be attributed to several practical advantages. The MAS is quick to administer—typically only a few minutes for multiple joints—and requires no specialized equipment or complex setup. A clinician can easily integrate the MAS into a routine exam—for example, by rapidly moving a patient's limb during a therapy session—without interrupting the flow of care. The procedure is generally well-tolerated by patients, even those with severe disability, because it simply involves passive limb movement performed by the examiner. Moreover, the MAS provides an accessible and standardized metric—its simple 0-to-4 scoring allows different clinicians and care teams to communicate about a patient's muscle tone status with a shared understanding of each score's significance.

The MAS is used across numerous neurological conditions characterized by spasticity. In stroke rehabilitation, MAS grades are recorded to track the emergence or resolution of limb spasticity as the patient recovers and to decide on interventions such as splinting or pharmacotherapy if high-tone impedes function. In spinal cord injury, MAS scores help quantify the degree of muscle tone increase below the level of injury, which is important because spastic hypertonia in spinal cord injury can affect mobility and caregiving needs and may warrant treatments such as botulinum toxin or baclofen. Although the MAS is commonly used in this population, clinicians recognize that spasticity in spinal cord injury is multifaceted, ranging from continuous tone to intermittent spasms. Similarly, in multiple sclerosis, periodic MAS assessments can gauge the effectiveness of anti-spastic medications and indicate when dosage adjustments or additional therapies are needed. In pediatric and adult cerebral palsy, the MAS is frequently part of the evaluation for muscle tone management; for example, a child with cerebral palsy may be assessed using the MAS before and after a round of botulinum toxin injections to quantify changes in muscle stiffness at the hamstrings or gastrocnemius. Indeed, in the context of cerebral palsy, precise measurement of spasticity—often using MAS or its alternatives—is critical for guiding interventions such as selective dorsal rhizotomy or orthopedic surgery.[17] 

The MAS can be used in almost any clinical setting without requiring specialized equipment, making it highly accessible in resource-limited settings and busy clinics. The test is brief, typically under 5 minutes, even when examining multiple muscle groups. This duration minimizes patient fatigue and allows frequent repetition to monitor progress. Another advantage is the scale's intuitive interpretation—higher scores directly correspond to a more pronounced tone, which is straightforward for clinicians to interpret and act upon. The MAS has also shown utility in monitoring treatment response—for example, a decrease in the MAS score after initiating an anti-spastic medication provides objective evidence of the treatment's effectiveness. Because of its widespread use over the decades, the MAS is backed by a large body of clinical experience and research. Clinicians are generally familiar with its scoring system, and there is a wealth of comparative data to contextualize an individual patient's score. In addition, the MAS is free and requires minimal training. Basic, brief instruction is typically sufficient for a healthcare provider to start using the scale. These factors have solidified the MAS as a convenient go-to tool for spasticity assessment in routine practice.

Notably, the MAS provides a limited view of spasticity, focusing only on the resistance felt during a single fast stretch of a muscle. However, spasticity is a complex phenomenon with multiple components. The MAS score does not capture aspects such as clonus (rhythmic jerking) or the frequency of spontaneous spasms that a patient experiences. For example, in an individual with spinal cord injury who has infrequent but strong leg spasms, the MAS—which measures tone at rest on passive movement—may yield a low score, even though the patient's spasticity impacts function through intermittent spasms. Similarly, the MAS does not distinguish between phasic spasticity (a brisk reflex-mediated catch) and tonic spasticity (sustained muscle stiffness). The MAS  effectively condenses all manifestations of increased tone into a single resistance score, leading to an oversimplification, as two patients with the same MAS score may have different spasticity profiles. The velocity-dependent nature of true spasticity presents a challenge, as the MAS is typically conducted at a single approximate high velocity of stretch. This approach fails to assess how tone may vary at different movement speeds. Some critics have pointed out that because the MAS uses only one velocity (often not precisely controlled), it does not fully adhere to Lance's conceptual definition of spasticity, which emphasizes changes in tone with varying velocity.[11] Furthermore, grading ambiguities exist within the MAS. The introduction of the 1+ grade, while improving sensitivity, created an extra decision point that examiners may interpret inconsistently. The exact difference between 1 and 1+ or 1+ and 2 can be subtle in practice.

The MAS is not the only tool available for the assessment of spasticity. The Tardieu Scale is another clinical scale that has gained favor, especially in pediatric spasticity assessments. The Tardieu Scale evaluates muscle response to passive stretch at different velocities, using 2 angular measurements—X_V1, representing the angle of catch during a slow stretch, and X_V3, indicating the angle of catch during a rapid stretch. The difference between these values (X = X_V1 − X_V3) defines the spasticity angle. In addition, a spasticity grade (Y), recorded as an ordinal value, reflects the presence or absence of a catch or clonus, distinguishing between fatigable and infatigable clonus responses.[11]

To address the subjectivity and ordinal limitations of MAS, researchers and clinicians have developed quantitative methods to assess spasticity. These approaches, including biomechanical and electrophysiological measurements, provide objective data. Such methods often require bulky equipment, technical expertise, and longer assessment times, limiting their use to research labs or specialized clinics. These approaches are not feasible for day-to-day rapid assessments in a hospital ward or a general therapy clinic. In routine clinical practice, a quick MAS examination is far more practical than setting up a dynamometer for each patient. Thus, while instrumented evaluations can validate and supplement the clinical scales—and are invaluable for research and complex cases—they have not replaced the MAS. Modern best practices often involve using the MAS in conjunction with other assessments to capture the multifaceted nature of spasticity. Notably, newer assessment modalities, including imaging techniques, such as elastography to measure muscle stiffness; wearable sensor systems to detect hypertonic movements; and remote assessments through telemedicine tools, are being explored, reflecting the ongoing evolution in spasticity measurement.[13] 

Nursing, Allied Health, and Interprofessional Team Interventions

Effective management of spasticity, as assessed by the MAS, requires a collaborative interprofessional approach to optimize patient-centered care. Clinicians, advanced practice providers, physical and occupational therapists, speech-language pathologists, and pharmacists contribute specialized expertise to address spasticity-related disability, functional limitations, and quality-of-life concerns.

Clinicians and advanced practice providers oversee diagnosis, treatment planning, and pharmacological interventions, including oral antispasticity agents, botulinum toxin injections, and intrathecal baclofen therapy.[18] These professionals collaborate with therapists to tailor rehabilitation strategies and monitor MAS scores to assess treatment efficacy. Nurses are crucial in monitoring spasticity, administering medication, educating patients on self-management strategies, and ensuring adherence to positioning and stretching programs to prevent complications, such as contractures and pressure ulcers. Physical and occupational therapists use targeted MAS assessments to design mobility training, passive stretching regimens, and adaptive device recommendations that enhance function and prevent joint stiffness. These professionals coordinate with speech-language pathologists when oromandibular spasticity affects swallowing or speech, ensuring safe feeding practices and communication strategies. Pharmacists contribute by optimizing medication regimens, identifying potential drug interactions, and monitoring for adverse effects.

Ethical considerations in spasticity management include ensuring informed consent, respecting patient autonomy in selecting interventions, and addressing equity in access to advanced therapies. Interprofessional communication is critical and includes aspects of standardized MAS scoring, shared decision-making through multidisciplinary rounds, and real-time electronic health record updates to ensure consistency in care. In addition, care transitions between acute, rehabilitation, and home settings should be well-coordinated to sustain long-term functional improvements.

Healthcare teams must emphasize fall prevention strategies, contracture management, pressure ulcer prevention, and caregiver education on daily exercises and medication adherence to enhance patient safety and outcomes.