Bracing and AFOs
- The fundamental principle of foot and ankle orthotics is to MATCH THE ORTHOSIS TO THE BIOMECHANICAL DEFICIT: an orthosis is chosen for what it must do - support, offload pressure, control a flexible or fixed deformity, substitute for weak muscles, or stabilise an unstable/arthritic joint - so understanding the patient's specific problem (and whether deformities are flexible or fixed) is the key to prescribing correctly.
- FOOT ORTHOSES (insoles) act on the foot itself: they support the arch, redistribute and OFFLOAD plantar pressure (with metatarsal pads/bars, heel cups/posts), accommodate fixed deformity and cushion - used for plantar fasciitis, metatarsalgia, flexible flatfoot and, importantly, OFFLOADING the at-risk/diabetic/insensate or ulcerated foot (total-contact/accommodative insoles), where evidence supports footwear/insoles for improving stability and gait.
- ANKLE-FOOT ORTHOSES (AFOs) control the ankle and foot through stance and swing; the simplest is the POSTERIOR LEAF SPRING (PLS) AFO, a flexible posterior AFO that provides DORSIFLEXION ASSIST in swing for a FLEXIBLE FOOT DROP (e.g. common peroneal nerve palsy, flexible neurological foot drop) while allowing some plantarflexion - dorsiflexion-assist orthoses/devices increase swing-phase dorsiflexion and alleviate drop-foot.
- A SOLID/RIGID AFO immobilises the ankle and is used for a FIXED deformity, significant instability, spasticity or pain that needs full control; a HINGED/articulated AFO permits controlled dorsiflexion (with a plantarflexion stop) - useful when some ankle motion is desirable, e.g. to allow tibial advance while blocking foot drop.
- A GROUND-REACTION (floor-reaction) AFO has an anterior tibial shell and a rigid footplate that, by resisting forward tibial advance in stance, generates a knee-extension moment - it substitutes for QUADRICEPS weakness and controls a CROUCH gait (e.g. in cerebral palsy or quadriceps insufficiency), provided there is no fixed knee-flexion contracture.
- SPECIALISED devices match specific pathologies: the ARIZONA (gauntlet) AFO - a lace-up leather AFO with rigid stays - controls the hindfoot and ankle for HINDFOOT/ANKLE ARTHRITIS and stage II-III adult-acquired flatfoot (posterior tibial tendon dysfunction); the CROW (Charcot Restraint Orthotic Walker) boot and total-contact casts/insoles OFFLOAD the CHARCOT or ulcerated/insensate foot to prevent and heal ulceration; and a PTB (patellar-tendon-bearing) AFO offloads the tibia/ankle - the overarching goals being to support, offload, control deformity, improve gait and prevent ulceration.
- “Match the orthosis to the deficit: FOOT ORTHOSES/insoles (support/offload/accommodate); AFOs control ankle/foot in stance + swing.
- “POSTERIOR LEAF SPRING AFO = flexible foot drop (dorsiflexion assist); SOLID/RIGID AFO = fixed deformity/instability/spasticity; HINGED = controlled dorsiflexion; GROUND-REACTION (floor-reaction) AFO = QUADRICEPS weakness/crouch (no fixed knee flexion).
- “ARIZONA/gauntlet AFO = hindfoot/ankle arthritis & PTTD; CROW boot / total-contact cast = CHARCOT/ulcerated foot offloading; PTB-AFO offloads the tibia. Goals: support, offload, control deformity, improve gait, prevent ulceration.
Posterior leaf spring AFO for flexible foot drop (dorsiflexion assist); ground-reaction AFO for quadriceps weakness/crouch (no fixed knee flexion).
Solid/rigid AFO for fixed deformity/instability; Arizona AFO for hindfoot/ankle arthritis & PTTD; CROW boot / total-contact for the Charcot/ulcerated foot (offload).
The Orthosis Matched to the Deficit
The governing principle is to match the orthosis to the biomechanical deficit. Foot orthoses/insoles support the arch, offload pressure (metatarsal pads, heel cups), accommodate fixed deformity and cushion - for plantar fasciitis, metatarsalgia, flexible flatfoot, and offloading the at-risk/ulcerated foot. AFOs control the ankle/foot: a posterior leaf spring (PLS) AFO gives dorsiflexion assist for flexible foot drop; a solid/rigid AFO controls a fixed deformity, instability or spasticity; a hinged AFO allows controlled dorsiflexion; and a ground-reaction (floor-reaction) AFO resists tibial advance to substitute for quadriceps weakness/crouch (needs no fixed knee-flexion contracture). Specialised devices: the Arizona (gauntlet) AFO for hindfoot/ankle arthritis and PTTD, and the CROW boot / total-contact cast/insoles to offload the Charcot or ulcerated foot. Goals: support, offload, control deformity, improve gait, and prevent ulceration.
| Orthosis | What it does | Typical indication |
|---|---|---|
| Foot orthosis / insole | Supports arch; offloads/redistributes pressure; accommodates deformity | Plantar fasciitis, metatarsalgia, flexible flatfoot, at-risk/ulcerated foot |
| Posterior leaf spring (PLS) AFO | Flexible; dorsiflexion assist in swing | Flexible foot drop (e.g. common peroneal palsy) |
| Solid / rigid AFO | Immobilises the ankle (full control) | Fixed deformity, instability, spasticity, pain |
| Hinged / articulated AFO | Allows controlled dorsiflexion (plantarflexion stop) | When some controlled ankle motion is desirable |
| Ground-reaction (floor-reaction) AFO | Anterior shell resists tibial advance -> knee-extension moment | Quadriceps weakness / crouch gait (no fixed knee flexion) |
| Arizona / gauntlet AFO | Lace-up rigid hindfoot/ankle control | Hindfoot/ankle arthritis; PTTD (adult-acquired flatfoot) |
| CROW boot / total-contact cast | Total-contact offloading of the foot | Charcot foot / neuropathic ulceration |
Prescribing Principles & Goals
- Define the deficit: Is the foot drop flexible or is there a fixed deformity? Is there instability, spasticity, quadriceps weakness, hindfoot/ankle arthritis, or an insensate/ulcerated (Charcot) foot?
- Foot drop: flexible -> posterior leaf spring AFO (dorsiflexion assist); needing more control/fixed -> solid/rigid or hinged AFO.
- Quadriceps weakness/crouch: ground-reaction (floor-reaction) AFO - but only if there is NO fixed knee-flexion contracture.
- Hindfoot/ankle arthritis or PTTD: Arizona/gauntlet AFO (or bracing) to control and offload.
- Charcot/insensate/ulcerated foot: total-contact cast/insole or CROW boot to OFFLOAD and prevent/heal ulceration.
- Goals: support, offload pressure, control deformity, improve gait efficiency, relieve pain and prevent ulceration - reviewing fit and skin to avoid pressure complications, especially in the insensate foot."
Two principles keep orthotic prescription safe and effective. First, MATCH the orthosis to the specific deficit and to whether deformities are flexible or fixed: a posterior leaf spring AFO that suits a flexible foot drop is inadequate for a fixed deformity or a spastic, unstable ankle (which need a solid or hinged AFO), and a ground-reaction AFO only works for quadriceps weakness/crouch if there is no fixed knee-flexion contracture - prescribing the wrong device wastes time and can worsen gait. Second, watch the SKIN, especially in the INSENSATE/diabetic or Charcot foot: orthoses and total-contact devices that offload pressure are central to preventing and healing neuropathic ulceration, but a poorly-fitting brace can itself cause pressure ulceration in a foot that cannot feel it, so fit, accommodation of bony prominences and regular skin review are essential. The overarching aim is to support, offload, control deformity and improve gait while doing no harm.
Evidence & Key Studies
Dorsiflexion-assist (ankle exosuit/AFO-type) device alleviating drop-foot in gait
- An assistive ankle device providing dorsiflexion assistance increased ankle dorsiflexion during swing phase, alleviating drop-foot on the more-affected side.
- Unlike a rigid orthosis that restricted push-off plantarflexion, the dorsiflexion-assist device enabled more typical push-off plantarflexion motion - illustrating the trade-off between rigid control and preserved motion.
- The findings illustrate the biomechanical goal of dorsiflexion-assist orthoses (correcting swing-phase foot drop) while highlighting limits on acutely changing muscle activity/energy cost.
Footwear and insoles for balance and gait in athletes with ankle injuries (systematic review protocol)
- Specialised footwear and insoles are widely used to enhance stability and normalise gait in athletes with acute or chronic ankle injuries and instability.
- The review will systematically evaluate footwear/insole interventions on balance and gait parameters, reflecting the role of foot orthoses in ankle instability.
- It underscores that orthotic interventions target postural control and gait mechanics (the rationale for their use).
According to PubMed, the biomechanical goal of dorsiflexion-assist orthoses/devices (increasing swing-phase dorsiflexion to alleviate foot drop, and the trade-off between rigid control and preserved push-off) comes from the cited Thurston study, and the rationale for footwear/insoles in improving balance and gait in ankle injury/instability from the cited Gasavi Nezhad review. The classification of AFOs (posterior leaf spring, solid/rigid, hinged, ground-reaction), the specialised devices (Arizona/gauntlet AFO, CROW boot, total-contact cast), and their matched indications (flexible foot drop, fixed deformity, quadriceps weakness/crouch, hindfoot/ ankle arthritis/PTTD, Charcot/ulcerated foot) are standard, well-established teaching. (See also our Charcot Neuroarthropathy and Posterior Tibial Tendon Dysfunction topics.)
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“How would you choose an ankle-foot orthosis for different problems - foot drop, fixed deformity, quadriceps weakness, and a Charcot foot?”
Mnemonics & Memory Aids
BRACE
Hook:BRACE: Biomechanical deficit match, Rigid for fixed deformity, Assist dorsiflexion (PLS)/Arizona for arthritis, Crouch -> ground-reaction / CROW for Charcot, Examine the skin.
Principle
- Match the orthosis to the biomechanical deficit (flexible vs fixed)
- Goals: support, offload, control deformity, improve gait, prevent ulceration
- Foot orthoses/insoles act on the foot; AFOs control the ankle/foot
AFO types
- Posterior leaf spring: flexible foot drop (dorsiflexion assist)
- Solid/rigid: fixed deformity, instability, spasticity; hinged: controlled dorsiflexion
- Ground-reaction (floor-reaction): quadriceps weakness/crouch (no fixed knee flexion)
Specialised devices
- Arizona/gauntlet AFO: hindfoot/ankle arthritis, PTTD (adult-acquired flatfoot)
- CROW boot / total-contact cast/insole: Charcot / neuropathic ulceration (offload)
- PTB-AFO: offload the tibia/ankle
Safety
- Wrong brace can worsen gait - match to deficit and flexibility
- Watch the skin in the insensate/diabetic/Charcot foot (pressure ulceration)
- Accommodate bony prominences; review fit regularly