ankle-foot orthosis (AFO)
/ AFO = A-F-O /
Watch someone with foot drop walk and you will see them hitch the hip up or swing the leg out, just to clear toes that no longer lift. The ankle-foot orthosis, almost always called an AFO, is the most commonly prescribed lower-limb brace. It is a device, usually moulded plastic, that wraps the back of the calf, the heel, and the sole, controlling the ankle and foot inside the shoe.
Its commonest job is to hold the foot up so the toes clear the ground in the swing phase of walking. In a solid (rigid) AFO, the ankle is locked level, which guarantees toe clearance but stops the natural ankle motion. A posterior leaf spring AFO is thinner and springier: it lets the foot drop a little under control after heel strike, then springs the toes back up to clear the ground — closer to natural walking. Others have a hinged ankle that blocks the foot from dropping but allows it to bend up, useful for someone who can push off but cannot lift. The choice depends on which movements must be stopped and which preserved.
AFOs show up constantly: after stroke, in cerebral palsy, in peripheral nerve injury, in multiple sclerosis. They can transform safety and energy cost — walking with dragging toes is exhausting and dangerous. But an AFO substitutes for the muscle; it does not retrain it, and a brace that is too rigid can let the calf and shin muscles weaken further. Fit is critical: a poorly trimmed AFO rubs the shin or the ankle bones and, in an insensate foot, can cause an unnoticed sore.
Six weeks after a stroke, a woman's left foot still drops and she catches it on stairs. A solid-ankle AFO inside her shoe holds the foot level; she climbs the clinic stairs without tripping, though she misses the natural spring of her ankle and the team continues to work on the muscle.
The most common lower-limb brace: it holds the foot up so the toes clear the ground when walking.
An AFO substitutes for weak muscle but does not retrain it; an over-rigid brace can let muscle weaken further. In a numb foot, a badly fitted AFO can cause a sore the person never feels.