modified Ashworth scale
/ ASH-werth /
After certain injuries to the brain or spinal cord, a limb can become stiff in a particular way: when someone tries to move it for you, it resists, sometimes catching and then giving way, like a pocket-knife that snaps shut. To talk usefully about how much of this stiffness there is, clinicians needed a simple shared ruler. The modified Ashworth scale is the most widely used one — a quick, hands-on way to grade how much a muscle resists being stretched.
The test is straightforward to perform: the examiner takes the relaxed limb and moves the joint through its range fairly briskly, feeling how much the muscle fights back. The result is scored on a short ladder. A score of 0 means no increase in resistance at all. A score of 1 means a slight catch at the end of the range. The next steps — written as 1-plus, 2, 3 — capture progressively more resistance, until a score of 4 means the limb is rigid and can barely be moved. Because it is fast and needs no equipment, it can be repeated at every visit to follow how a treatment like stretching, oral medication, or a botulinum toxin injection is changing the tone.
Two honest cautions come with this scale. First, what it measures is resistance to passive movement, which mixes true spasticity (a velocity-dependent neural reflex) together with non-neural stiffness from tight, shortened tissues — it does not cleanly separate the two, which is why the Tardieu scale, that adds the speed of stretch, is sometimes preferred. Second, and more important clinically, a high score is not automatically a problem to be erased: some people lean on their stiff leg to stand, and removing all of that tone can leave them weaker and less safe. The number guides treatment; it does not dictate it.
A woman after a stroke has a modified Ashworth score of 3 at the elbow, so it stays bent and is hard to wash under. After a botulinum toxin injection it drops to 1, the arm opens, and hygiene becomes easier — but the team first checks she was not relying on that tone to support her wrist.
A lower tone score is only a good outcome if the function it served is not lost.
A common mistake is treating a higher Ashworth score as automatically worse: not all spasticity should be reduced, because some people use their tone to stand or transfer, and over-treatment can trade stiffness for weakness.