Table of Contents
Ashworth Scale / Modified Ashworth Scale
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About Ashworth Scale / Modified Ashworth Scale
Scale Name
Ashworth Scale / Modified Ashworth Scale
Author Details
Richard Bohannon PT, PhD and Melissa Smith, PT
Translation Availability
Not Sure
Background/Description
At its initial stages, the Ashworth Scale was designed to examine the effects of antispasticity drugs on spasticity in Multiple Sclerosis (MS). The purpose of the Modified Ashworth Scale (MAS) was to measure spasticity in patients with lesions of the central nervous system.
In the original Ashworth Scale, resistance to passive movement about a joint with varying degrees of velocity is measured on a scale of 0 (no resistance) to 4 (rigidity). In the modified Ashworth Scale, a 1+ scoring category is added to indicate resistance through less than half of the movement (Bohannon & Smith, 1987).
The Ashworth Scale has a two-part history, reflecting its development and refinement. In the 1960s, Dr. Bryan Ashworth introduced the original Ashworth Scale while working with multiple sclerosis patients. This initial version aimed to grade spasticity, a condition causing increased muscle tone and tightness. It functioned as a simple 5-point scale, ranging from 0 (no resistance) to 4 (limb completely rigid).
Recognizing the need for finer gradations, especially for milder spasticity, the Ashworth Scale was modified in 1987 by Bohannon and Smith. This modification introduced the now-common “Modified Ashworth Scale” (MAS). The MAS added a key element: a score of “1+”. This in-between category captured slight increases in muscle tone that were only present for a brief moment during movement. This addition improved the scale’s sensitivity in detecting even subtle changes in spasticity.
The MAS remains a widely used tool in clinical settings. It’s a quick and easy assessment method requiring no special equipment. A healthcare professional will passively move a joint through its range of motion while grading the resistance encountered based on the 6-point MAS scale. This allows them to evaluate spasticity in various joints, though it’s most commonly used for limbs.
While valuable, it’s important to remember that the MAS is subjective. Different healthcare professionals might assign slightly different scores due to variations in how they perform the test and interpret resistance. However, the standardized scale provides a common language for clinicians to communicate and track changes in spasticity over time.
Administration, Scoring and Interpretation
- Patient Positioning: The patient is positioned comfortably, typically supine (lying on their back) for easier limb examination. The specific position might vary depending on the joint being assessed.
- Relaxation: The healthcare professional will instruct the patient to relax and avoid actively resisting the movement.
- Joint Selection: The healthcare professional identifies the specific joint they want to assess for spasticity. This could be an elbow, knee, ankle, or any other major joint.
- Passive Movement: The professional gently grasps the limb segment distal (further away) to the joint and slowly moves it through its full range of motion. This movement should be done at a moderate speed, often described as “one-thousand-and-one” speed.
- Resistance Evaluation: During the passive movement, the healthcare professional assesses the resistance encountered from the muscles opposing the movement. This resistance indicates the degree of spasticity.
Reliability and Validity
The reliability and validity of the Ashworth Scale, particularly the Modified Ashworth Scale (MAS), are somewhat complex. Here’s a breakdown:
- Intrarater reliability: This refers to the consistency of a single rater in scoring the scale across time. Studies have shown mixed results, with some indicating good intrarater reliability, meaning a healthcare professional gets similar scores when retesting the same patient.
- Inter-rater reliability: This refers to the consistency of scoring between different healthcare professionals. Here, research suggests the MAS is less reliable. Different examiners might assign slightly different scores due to variations in how they perform the test and interpret resistance.
- Content validity: The scale’s content (grading muscle tone) seems relevant to assessing spasticity.
- Criterion validity: This refers to how well the MAS score compares to a “gold standard” measure of spasticity. Unfortunately, there’s no definitive gold standard for spasticity, making it difficult to assess the MAS’s criterion validity definitively.
Available Versions
Maltiple-Items
Reference
Bohannon, R. W., & Smith, M. B. (1987). Interrater reliability of a modified Ashworth scale of muscle spasticity. Physical therapy, 67(2), 206-207.
Bohannon, R. and Smith, M. (1987). “Inter rater reliability of a modified Ashworth scale of muscle spasticity.” Physical Therapy 67(2): 206.
Brashear, A., Zafonte, R., et al. (2002). “Inter-and intrarater reliability of the Ashworth Scale and the Disability Assessment Scale in patients with upper-limb poststroke spasticity* 1.” Archives of physical medicine and rehabilitation 83(10): 1349-1354.
Gregson, J., Leathley, M., et al. (1999). “Reliability of the Tone Assessment Scale and the modified Ashworth scale as clinical tools for assessing poststroke spasticity.” Archives of physical medicine and rehabilitation 80(9): 1013-1016. Find it on PubMed
Gregson, J., Leathley, M., et al. (2000). “Reliability of measurement of muscle tone and muscle power in stroke patients.” Age and Ageing 29(3): 223.
Haas, B., Bergström, E., et al. (1996). “The inter rater reliability of the original and of the modified Ashworth scale for the assessment of spasticity in patients with spinal cord injury.” Spinal Cord 34(9): 560-564.
Important Link
Scale File:
Frequently Asked Questions
What is the Ashworth Scale?
A tool to measure muscle stiffness (spasticity).
What are the different versions?
Original Ashworth Scale (5 points)
Modified Ashworth Scale (MAS) – more common (6 points with a “1+” category)
How is it administered?
Healthcare professional moves your limb and scores resistance (0-4).
What do the scores mean?
0: No increased tone
1+: Slight, brief increase
1-4: Increasing resistance to movement
Is it reliable?
Somewhat – consistent scoring can vary between testers.
Is it valid?
Content validity is good (measures what it intends to).
Criterion validity is difficult to assess (no gold standard for spasticity).
Why is it still used?
Simple, easy to use, standardized scale.
Detects subtle changes in spasticity.
Limitations?
Subjective – scoring can vary between testers.
Shouldn’t be the only assessment tool.
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