Tardieu scale
/ tar-DYUH /
Imagine you want to know not just 'how stiff is this limb?' but specifically 'how much of the stiffness is the reflex grabbing, and how much is the muscle simply being too short?' The modified Ashworth scale, the common bedside measure, lumps these together. The Tardieu scale was designed to pull them apart, by cleverly using the one thing that defines spasticity — its dependence on the speed of movement.
The trick is to move the same joint at two speeds. First the examiner moves it very slowly and records how far the joint can go before tissue stops it — this slow range reflects the true, mechanical length of the muscle (called R2). Then the examiner moves it fast and notes the angle where the reflex suddenly catches the limb — the 'catch' angle (called R1). The examiner also rates the quality of that catch, from none, to a clear catch that releases, to clonus. The gap between the two angles, R2 minus R1, is the key output: a big gap means a lot of dynamic, reflex-driven spasticity that a nerve-acting treatment might relax; a small gap means most of the stiffness is fixed shortening that needs stretching or surgery instead.
In rehabilitation the Tardieu scale is valued because it answers a treatment-shaping question the Ashworth cannot: it separates the part of the problem that botulinum toxin or stretching can change from the part that is already a contracture, and it gives a target angle to track over time. Its weaknesses are practical — it takes longer, demands a consistent fast and slow speed, and gives less reliable numbers between different examiners — so many clinics use the quick Ashworth for screening and reserve the Tardieu for planning focal treatment.
Assessing a spastic calf, a therapist finds the ankle reaches a near-normal angle when moved very slowly (R2) but catches sharply much earlier when moved fast (R1). The large gap between them tells her there is real reflex spasticity to target with a botulinum injection, rather than a tendon that has already shortened beyond saving.
Slow range (R2) minus fast catch angle (R1) separates dynamic spasticity from fixed shortening.
The Tardieu's advantage over the Ashworth — separating reflex from contracture — depends entirely on holding the slow and fast speeds consistent. Sloppy, variable speeds erase the very information the scale exists to capture.