Which AFO should not be used in the presence of spasticity due to its coil spring mechanism?

• A. AFO: Posterior leaf spring
• B. AFO: Varus Correction strap
• C. AFO: Dorsiflexion spring assist (Klenzak Joint)
• D. AFO: Metal anterior stop

Answer: (C)

Spasticity makes muscles respond more to rapid stretches, so you want an AFO that doesn’t cause a quick, forceful change in ankle position. A dorsiflexion assist that uses a coil spring actively and rapidly pulls the foot into dorsiflexion during swing can provoke a spastic response in the plantarflexors, leading to unpredictable ankle motion, toe drag, or gait instability. Because the spring mechanism introduces that abrupt dorsiflexion, it’s avoided when spasticity is present.

Other options provide more controlled or static alignment without forcing a rapid stretch: a posterior leaf spring offers a softer, dynamic dorsiflexion assist with less abrupt movement; a varus correction strap simply tunes hindfoot alignment without driving joint motion; a metal anterior stop limits motion to prevent excessive dorsiflexion.