Ankle Foot Orthosis Tuning Principles in Children with Cerebral Palsy
Top Contributors - Ewa Jaraczewska, Jess Bell and Tarina van der Stockt
Introduction
Ankle-foot-orthoses (AFOs) are often prescribed for ambulant children with cerebral palsy (CP) who are classified as levels I-III on the Gross Motor Function Classification System (GMFCS).[1] AFO use is believed to confer a range of benefits, including improved gait (e.g. increased step length, walking speed and decreased cadence), energy efficiency, balance, and stability.[1][2] Orthotic prescription should always align with the child or their family's treatment goals,[3] and individualised tuning is important.[4]
Normal Gait and Pathological Gait Patterns in Cerebral Palsy
The normal gait cycle consists of heel strike, loading response, mid-stance, terminal stance and push-off, swing, back to initial contact, and preparation for initial contact.
During each phase of the gait cycle, specific limb positions are expected. At initial contact, the knee should be fully extended. As the foot hits the ground during loading response, there should be slight knee flexion. As the leg moves through mid-stance, the knee moves from extension to a neutral position, with the foot going into dorsiflexion. In terminal stance, the foot is in plantar flexion for push-off. During swing phase, the foot undergoes dorsiflexion once again, allowing for ground clearance. Finally, in terminal swing, the limb is positioned in a dorsiflexed state, preparing for heel strike once more.[5]
For detailed information on the gait cycle, you might be interested in reading this optional article: The Gait Cycle.
Common Pathological Gait Patterns in Cerebral Palsy
Children with cerebral palsy may exhibit several common pathological gait patterns. One such pattern is true equinus, characterised by equinus at the ankle (child is fully up on their toes) and neutral alignment of the hip and knee.[5]
Another potential gait pattern is jump gait, which involves equinus at the ankle as well as flexion of both the hip and knee. Apparent equinus is also a possible gait pattern in children with cerebral palsy. In this case, although the ankle is in neutral position, the child is up on their toes because of excessive hip and knee flexion.[5]
Finally, crouch gait can occur when there is excessive dorsiflexion of the foot accompanied by flexion of both the hip and knee.[5]
Functional Gait Analysis for AFO Tuning
During a functional gait analysis, an orthotist will assess for comfort, obtain the patient's feedback and perform a visual observation, including looking at leg length.
During the visual observational gait analysis, they may look at the following parameters:[5]
- temporal-spatial parameters: walking speed, step length, ground clearance, and the presence of tripping or falling.
- stance phase analysis: at initial contact, the presence and quality of heel strike and the weight acceptance pattern; during weight transfer, looking for any asymmetrical weight bearing.
- lower limb alignment: assessing for below-knee rotation and hip rotation patterns, and clearance during the swing phase of gait.
- proximal joint control: at the trunk, assessing vertical alignment and looking for stability during gait; at the pelvis, assessing whether it is level and looking at dynamic control during walking; and at the hip and knee, the timing of extension and the movement quality throughout the gait cycle.
Rigid Ankle Foot Orthoses-Footwear Combination (AFO-FC) Tuning
AFO-footwear combination (AFO-FC) tuning "can be defined as the process whereby fine adjustments are made to the design of the AFO-FC to optimise its performance during a particular activity. Biomechanical optimisation encompasses the whole process of designing, aligning and tuning the AFO-FC."[6]
It is important to remember that ankle dorsiflexion and plantar flexion are blocked in a rigid AFO, thus movement compensation at other joints is required.
Goals of AFO-FC Tuning
Key goals of the AFO-FC tuning process include optimising lower-limb alignment and reducing energy expenditure during gait.
AFO-FC Tuning Principles
"Alignment of the ground reaction force (GRF) relative to the joints throughout normal gait is key to producing a controlled, energy efficient gait."[7]
There is evidence that, in children with hip and knee mobility, "tuning" AFOs through posting, wedging and footwear can influence ground reaction forces and improve a child's hip and knee position during gait.[5]
The following examples highlight how an AFO-FC may change the kinetics and kinematics of the gait of a child with CP.[5]
AFO set in plantar flexion: the AFO is reclined and remains reclined in a shoe. If a child wears this AFO and attempts to stand or walk, they will be pushed into knee hyperextension. However, tightness in either their gastrocnemius or their hamstrings will prevent them from achieving a hyperextended position. As a result, the child will be forced to go up onto their toes, creating an unstable standing position. Correct posting of the AFO would help prevent this.
AFO set in dorsiflexion: the AFO is inclined, which increases when the AFO is placed in a shoe. This positioning would encourage a crouch gait and knee flexion. Correct posting or wedging would help prevent this.
Elements of AFO-FC Tuning
When tuning an AFO, the orthotist will aim to choose the most appropriate design and material to control the foot and ankle in three planes.[7] The main areas of focus are set out below.
The angle of the ankle in the AFO (AAAFO) is the angle of the foot relative to the shank in the sagittal plane in the AFO.[5] The fixed ankle angle of the AFO might be in dorsiflexion, in a plantigrade position at 90 degrees, or in plantar flexion, and the AAAFO should accommodate gastrocnemius shortening.[7]
Bench alignment concerns where the AFO sits on the bench and whether it is vertical, reclined, or inclined. The optimum bench-to-vertical alignment is generally around 90 degrees, with posting.[5]
AFO and footwear (AFO-FC) heel height is also considered. The shoe heel height, or the heel sole differential, influences the angle of the AFO, and this becomes the shank-to-vertical angle in standing.[7]
The shank-to-vertical angle (SVA) is the angle of the shank relative to the vertical, measured in the sagittal plane with the child standing in the AFO. The line at the front of the tibia represents the line of the shank. The SVA is described as inclined if the shank is angled forward from the vertical and reclined if it is angled backwards from the vertical. It is described in degrees, with the vertical being 0°; for example, a plantarflexed ankle will be in a reclined position unless posting is added. The amount of posting and the position of the forefoot and heel determines the inclination of the AFO. It may also be necessary to accommodate fixed deformities when fitting an AFO. For example, if a child presents with a ten-degree knee flexion contracture, posting can be added to enable the child's foot to be flat on the ground. The goal is to accommodate the fixed flexion position while considering the optimum SVA.[7]
"During midstance, an element of tibial inclination is required during normal gait. Thus, having an ankle complex and SVA fixed at 90° (when heel/ground contact is maintained) cannot achieve an optimal gait pattern as it prevents the shank from the necessary inclination required. Therefore, it must be recognised that the AAAFO and the SVA are independent of each other and require individual assessments of the patient."[7]
Case Examples
An 8-year-old child with bilateral cerebral palsy, GMFCS Level I, has an angle of the ankle in the AFO (AAAFO) of 90-5° on the right side and 90-8° on the left side. In the initial condition in the AFO, the shank-to-vertical angle (SVA) was 0°, causing slight knee hyperextension. Adding a 10mm wedge increased the SVA to 8°, optimising knee alignment.
Introduction
Ankle-foot-orthoses (AFOs) are often prescribed for ambulant children with cerebral palsy (CP) who are classified as levels I-III on the Gross Motor Function Classification System (GMFCS).[1] AFO use is believed to confer a range of benefits, including improved gait (e.g. increased step length, walking speed and decreased cadence), energy efficiency, balance, and stability.[1][2] Orthotic prescription should always align with the child or their family's treatment goals,[3] and individualised tuning is important.[4]
Normal Gait and Pathological Gait Patterns in Cerebral Palsy
The normal gait cycle consists of heel strike, loading response, mid-stance, terminal stance and push-off, swing, back to initial contact, and preparation for initial contact.
During each phase of the gait cycle, specific limb positions are expected. At initial contact, the knee should be fully extended. As the foot hits the ground during loading response, there should be slight knee flexion. As the leg moves through mid-stance, the knee moves from extension to a neutral position, with the foot going into dorsiflexion. In terminal stance, the foot is in plantar flexion for push-off. During swing phase, the foot undergoes dorsiflexion once again, allowing for ground clearance. Finally, in terminal swing, the limb is positioned in a dorsiflexed state, preparing for heel strike once more.[5]
For detailed information on the gait cycle, you might be interested in reading this optional article: The Gait Cycle.
Common Pathological Gait Patterns in Cerebral Palsy
Children with cerebral palsy may exhibit several common pathological gait patterns. One such pattern is true equinus, characterised by equinus at the ankle (child is fully up on their toes) and neutral alignment of the hip and knee.[5]
Another potential gait pattern is jump gait, which involves equinus at the ankle as well as flexion of both the hip and knee. Apparent equinus is also a possible gait pattern in children with cerebral palsy. In this case, although the ankle is in neutral position, the child is up on their toes because of excessive hip and knee flexion.[5]
Finally, crouch gait can occur when there is excessive dorsiflexion of the foot accompanied by flexion of both the hip and knee.[5]
Functional Gait Analysis for AFO Tuning
During a functional gait analysis, an orthotist will assess for comfort, obtain the patient's feedback and perform a visual observation, including looking at leg length.
During the visual observational gait analysis, they may look at the following parameters:[5]
- temporal-spatial parameters: walking speed, step length, ground clearance, and the presence of tripping or falling.
- stance phase analysis: at initial contact, the presence and quality of heel strike and the weight acceptance pattern; during weight transfer, looking for any asymmetrical weight bearing.
- lower limb alignment: assessing for below-knee rotation and hip rotation patterns, and clearance during the swing phase of gait.
- proximal joint control: at the trunk, assessing vertical alignment and looking for stability during gait; at the pelvis, assessing whether it is level and looking at dynamic control during walking; and at the hip and knee, the timing of extension and the movement quality throughout the gait cycle.
Rigid Ankle Foot Orthoses-Footwear Combination (AFO-FC) Tuning
AFO-footwear combination (AFO-FC) tuning "can be defined as the process whereby fine adjustments are made to the design of the AFO-FC to optimise its performance during a particular activity. Biomechanical optimisation encompasses the whole process of designing, aligning and tuning the AFO-FC."[6]
It is important to remember that ankle dorsiflexion and plantar flexion are blocked in a rigid AFO, thus movement compensation at other joints is required.
Goals of AFO-FC Tuning
Key goals of the AFO-FC tuning process include optimising lower-limb alignment and reducing energy expenditure during gait.
AFO-FC Tuning Principles
"Alignment of the ground reaction force (GRF) relative to the joints throughout normal gait is key to producing a controlled, energy efficient gait."[7]
There is evidence that, in children with hip and knee mobility, "tuning" AFOs through posting, wedging and footwear can influence ground reaction forces and improve a child's hip and knee position during gait.[5]
The following examples highlight how an AFO-FC may change the kinetics and kinematics of the gait of a child with CP.[5]
AFO set in plantar flexion: the AFO is reclined and remains reclined in a shoe. If a child wears this AFO and attempts to stand or walk, they will be pushed into knee hyperextension. However, tightness in either their gastrocnemius or their hamstrings will prevent them from achieving a hyperextended position. As a result, the child will be forced to go up onto their toes, creating an unstable standing position. Correct posting of the AFO would help prevent this.
AFO set in dorsiflexion: the AFO is inclined, which increases when the AFO is placed in a shoe. This positioning would encourage a crouch gait and knee flexion. Correct posting or wedging would help prevent this.
Elements of AFO-FC Tuning
When tuning an AFO, the orthotist will aim to choose the most appropriate design and material to control the foot and ankle in three planes.[7] The main areas of focus are set out below.
The angle of the ankle in the AFO (AAAFO) is the angle of the foot relative to the shank in the sagittal plane in the AFO.[5] The fixed ankle angle of the AFO might be in dorsiflexion, in a plantigrade position at 90 degrees, or in plantar flexion, and the AAAFO should accommodate gastrocnemius shortening.[7]
Bench alignment concerns where the AFO sits on the bench and whether it is vertical, reclined, or inclined. The optimum bench-to-vertical alignment is generally around 90 degrees, with posting.[5]
AFO and footwear (AFO-FC) heel height is also considered. The shoe heel height, or the heel sole differential, influences the angle of the AFO, and this becomes the shank-to-vertical angle in standing.[7]
The shank-to-vertical angle (SVA) is the angle of the shank relative to the vertical, measured in the sagittal plane with the child standing in the AFO. The line at the front of the tibia represents the line of the shank. The SVA is described as inclined if the shank is angled forward from the vertical and reclined if it is angled backwards from the vertical. It is described in degrees, with the vertical being 0°; for example, a plantarflexed ankle will be in a reclined position unless posting is added. The amount of posting and the position of the forefoot and heel determines the inclination of the AFO. It may also be necessary to accommodate fixed deformities when fitting an AFO. For example, if a child presents with a ten-degree knee flexion contracture, posting can be added to enable the child's foot to be flat on the ground. The goal is to accommodate the fixed flexion position while considering the optimum SVA.[7]
"During midstance, an element of tibial inclination is required during normal gait. Thus, having an ankle complex and SVA fixed at 90° (when heel/ground contact is maintained) cannot achieve an optimal gait pattern as it prevents the shank from the necessary inclination required. Therefore, it must be recognised that the AAAFO and the SVA are independent of each other and require individual assessments of the patient."[7]
Case Examples
An 8-year-old child with bilateral cerebral palsy, GMFCS Level I has an angle of the ankle in the AFO (AAAFO) of 90-5° on the right side and 90-8° on the left side. In the initial condition in the AFO, the shank-to-vertical angle (SVA) was 0°, causing slight knee hyperextension. Adding a 10mm wedge increased the SVA to 8°, optimising knee alignment.
During barefoot walking, an 11-year-old with unilateral right-sided cerebral palsy, GMFCS Level I, had initial contact with the forefoot, and the ground reaction force was too anterior. An AAAFO of 90-15° was used to control his foot position, and he had an SVA of 8° (inclined). When walking in the AFO, the ground reaction force position at the foot and knee improved.
A 13-year-old with bilateral cerebral palsy, GMFCS Level II, presents with a combination of crouch and jump gait. He has had multi-level surgery, has lower limb spasticity, especially around his knees, and has bilateral rigid AFOs. The AAAFO is set to an angle of 90-10°, posted to 10° forward inclination (90+10) to accommodate tightness in his hamstrings and gastrocnemius. This helps maintain (i.e. not increase) his crouch position and prevent further knee or hip flexion. The goal was to avoid deterioration and maintain upright walking ability.
A 10-year-old with bilateral cerebral palsy, GMFCS Level II, presents with a complex gait pattern with crouch gait. Bilateral rigid AFOs help control foot position and provide some knee or hip extension, though it is not possible to fully correct the internal rotation, valgus, and crouched gait pattern.
Conclusion
When working with children with cerebral palsy, we have to remember that it is an "ever-changing picture". While there may be some general improvements in children aged up to six to eight years old, there may be some deterioration during the growing years. It is essential to remember that no single solution will work at all times. There is often compromise. Orthotists must continually review, reassess and renew.[5]
During barefoot walking, an 11-year-old with unilateral right-sided cerebral palsy, GMFCS Level I, had initial contact with the forefoot, and the ground reaction force was too anterior. An AAAFO of 90-15° was used to control his foot position, and he had an SVA of 8° (inclined). When walking in the AFO, the ground reaction force position at the foot and knee improved.
A 13-year-old with bilateral cerebral palsy, GMFCS Level II, presents with a combination of crouch and jump gait. He has had multi-level surgery, has lower limb spasticity, especially around his knees, and has bilateral rigid AFOs. The AAAFO is set to an angle of 90-10°, posted to 10° forward inclination (90+10) to accommodate tightness in his hamstrings and gastrocnemius. This helps maintain (i.e. not increase) his crouch position and prevent further knee or hip flexion. The goal was to avoid deterioration and maintain upright walking ability.
A 10-year-old with bilateral cerebral palsy, GMFCS Level II, presents with a complex gait pattern with crouch gait. Bilateral rigid AFOs help control foot position and provide some knee or hip extension, though it is not possible to fully correct the internal rotation, valgus, and crouched gait pattern.
Conclusion
When working with children with cerebral palsy, we have to remember that it is an "ever-changing picture". While there may be some general improvements in children aged up to six to eight years old, there may be some deterioration during the growing years. It is essential to remember that no single solution will work at all times. There is often compromise. Orthotists must continually review, reassess and renew.[5]
Resources
- How does a systematic tuning protocol for ankle foot orthosis-footwear combinations affect gait in children in cerebral palsy?
- AFO tuning: Balancing function and satisfaction
- Orthotics in Cerebral Palsy
References
- ↑ 1.0 1.1 1.2 1.3 Everaert L, Papageorgiou E, Van Campenhout A, Labey L, Desloovere K. The influence of ankle-foot orthoses on gait pathology in children with cerebral palsy: A retrospective study. Gait Posture. 2023 Feb;100:149-156.
- ↑ 2.0 2.1 Alsultan F, Albarrak JB, Alshayie RA, Aloraini SM. Therapeutic effects of ankle-foot orthoses among children and adolescent with cerebral palsy: an overview of systematic reviews. Physical Therapy Reviews. 2025;30(6):415–28.
- ↑ 3.0 3.1 Dailey AH, Anderson S, Dillon MP. Exploring the rationale for prescribing ankle-foot orthoses and supramalleolar orthoses to children with cerebral palsy among pediatric orthotists in Australia. Prosthet Orthot Int. 2025 Oct 1;49(5):475-484.
- ↑ 4.0 4.1 Gasavi Nezhad Z, Vafayi AR, Arazpour M. The effect of ankle-foot orthoses and their characteristics on balance, and postural control in children with cerebral palsy: a systematic review. Health Sci Rep. 2026 Jun 7;9(6):e72613.
- ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 5.18 5.19 Fisher D. Optimising Orthotic Effectiveness in Ambulant Cerebral Palsy Course. Plus, 2024.
- ↑ 6.0 6.1 Owen E. Paediatric gait analysis and orthotic management with AFO footwear combinations. Course manual, 2012 (personal communication 16 April 2012).
- ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 Eddison N, Chockalingam N. The effect of tuning ankle foot orthoses-footwear combination on the gait parameters of children with cerebral palsy. Prosthet Orthot Int. 2013 Apr;37(2):95-107.