Modified Ashworth Scale Calculator
Grade spasticity and muscle tone across upper and lower extremity muscle groups. Includes clonus and contracture flags, intensity classification, and EMR-ready neurological documentation.
Clinically reviewed by Dr. Nikhil Mahajan, PT, MPT · Jan 15, 2025Perform passive movement at the speed of gravity (approximately 1 second per joint). Consistent speed is critical for reliable, comparable scores.
Upper Extremity
7 muscle groups — passive movement at speed of gravity
Lower Extremity
7 muscle groups — include hip, knee and ankle
Additional Clinical Signs
Modified Ashworth Scale Grade Reference
| Grade | Description | Clinical Characteristics | Typical Intervention |
|---|---|---|---|
| 0 | No increase in tone | Passive movement meets no resistance throughout ROM | No pharmacological intervention needed |
| 1 | Slight increase — catch at end ROM | Brief catch and release at end of ROM only | Stretching program, positioning |
| 1+ | Catch then resistance <50% ROM | Catch followed by minimal resistance through <half of ROM | Stretching, splinting, oral medication consideration |
| 2 | Marked increase — limb movable | Resistance throughout most of ROM; limb still easily moved | Oral antispasmodics, Botox consideration |
| 3 | Considerable increase — movement difficult | Passive movement is difficult; significant resistance throughout | Botox / Baclofen threshold — pharmacological intervention often required |
| 4 | Rigid in flexion or extension | Affected part rigid; passive movement nearly impossible | Intrathecal baclofen, surgical neurectomy, intensive management |
What is the Modified Ashworth Scale?
The Modified Ashworth Scale (MAS) is a 6-point ordinal clinical assessment tool used to grade spasticity and muscle tone by measuring resistance felt during passive movement of a limb through its range of motion. Originally developed as the Ashworth Scale in 1964, it was modified by Bohannon and Smith (1987) to add the intermediate grade 1+ — creating the current 6-level scale. The MAS is the most widely used clinical spasticity assessment tool in neurological rehabilitation, used to evaluate patients with stroke, spinal cord injury, multiple sclerosis, cerebral palsy, and traumatic brain injury.
Understanding MAS Grade 1+
The 1+ grade is the most clinically important modification from the original scale. It distinguishes between:
- Grade 1 — A catch that occurs only at the very end of ROM and then releases. The limb moves freely through most of its range.
- Grade 1+ — A catch that is followed by sustained but minimal resistance through less than half of the remaining ROM. This indicates more persistent but still mild hypertonia.
This distinction is clinically significant because grade 1+ often warrants intervention (stretching, splinting, oral medication) while grade 1 typically does not.
How to Administer the MAS
- Speed: Passive movement must be performed at a consistent speed — approximately the speed of gravity (1 second per joint movement). Spasticity is velocity-dependent; faster movement elicits more response, slower movement less.
- Position: Patient must be in a standardized, comfortable position. Arousal level, pain, and body temperature all affect spasticity scores.
- Direction: For flexor spasticity (most common post-stroke), move from flexion to extension. Document the direction clearly.
- Timing: Assess in the morning and at rest for consistent baseline measurements. Spasticity varies throughout the day.
- Documentation: Record specific muscle group, grade, side (left/right), position, and any additional signs (clonus, clonus beats, contracture).
Clinical Applications & Populations
- Post-stroke spasticity — Most common application; affects ~40% of stroke survivors. Elbow flexors and wrist flexors most commonly affected in UE; plantarflexors in LE.
- Spinal cord injury — Documents both upper and lower extremity tone; guides antispasticity medication titration.
- Multiple sclerosis — Monitors tone fluctuation with disease progression and heat sensitivity.
- Cerebral palsy — Used in pediatric populations to justify and monitor Botulinum toxin injections and surgical outcomes (SDR, ITB pump).
- Traumatic brain injury — Guides early splinting decisions and antispasticity pharmacology in ICU and rehabilitation phases.
MAS Score ≥ 3 — US Insurance Threshold
In the US healthcare system, documented MAS scores of 3 or above are often required by insurance providers as a prerequisite for authorization of:
- Botulinum toxin (Botox) injections — For focal spasticity reduction in specific muscle groups
- Intrathecal baclofen pump — For generalized spasticity affecting multiple limbs
- Phenol nerve block / surgical neurectomy — For severe, refractory spasticity
Accurate MAS documentation with specific muscle-group grades and functional impact descriptions is essential for insurance authorization letters.
Reliability & Limitations
- Interrater reliability: ICC = 0.82–0.87 when performed by trained clinicians using standardized speed and positioning
- Test-retest reliability: ICC = 0.75–0.85 — moderate; improves significantly with training
- Ordinal scale limitation: MAS grades are not equally spaced — the difference between grade 1 and 2 is not the same clinical magnitude as between 3 and 4
- Velocity dependency: Inconsistent movement speed is the single biggest source of measurement error — always use gravity speed
- MAS ≠ strength: High spasticity grade can coexist with severe muscle weakness (paresis). Do not confuse tone assessment with muscle strength testing.
MAS vs Other Spasticity Measures
- vs Tardieu Scale: The Tardieu Scale is more sensitive to spasticity vs contracture distinction, using two speeds (slow and fast) to differentiate neural and non-neural components. MAS is faster to administer; Tardieu is more diagnostically specific.
- vs Penn Spasm Frequency Scale: Penn measures frequency of spasm episodes, not passive resistance. MAS and Penn are complementary — use both for comprehensive spasticity documentation.
- vs Fugl-Meyer Assessment: FMA measures overall motor recovery including synergy patterns and coordination; MAS specifically measures tone/spasticity. Both are used together in stroke rehabilitation.