The proposed study evaluates the effect of ankle foot orthosis (AFO) heel height and stiffness on the forces and motion of the lower limb during over-ground walking in individuals who use an AFO for daily walking. Previous studies suggest that heel height and stiffness effect limb loading, but these data and the analysis techniques applied are limited. In this study, heel cushions with different height and stiffness's (4 conditions) will be placed in participants shoes and they will walk at controlled and self-selected speeds. Participants will also walk with their AFO as configured prior to enrollment, and with no AFO if possible. The proposed study will provide evidence that can be used by clinicians and researchers to align braces that most effectively improve function during every-day walking.

In this study the investigators to evaluate the effect of ankle foot orthosis (AFO) heel height and stiffness on the forces and motion of the lower limb during over-ground walking in individuals who use an AFO for daily walking. Previous studies suggest that heel height and stiffness effect limb loading, but these data and the analysis techniques applied are limited.

Two groups of subjects with impairments below the knee, that result in functional deficits and require daily AFO use, will be recruited for this study. The first group will have unilateral deficits associated with musculoskeletal injury or disease (Group 1), and the second group will have bilateral or unilateral deficits associated with peripheral nervous system disease (Group 2).

Lower limb forces and body motion will be assessed using computerized motion capture and force plates in the floor, as individuals walk over-ground. Small reflective markers placed on the participant's skin and force measuring plates in the floor will be used. Participants will walk with their clinically provided AFO, with added heel cushions of two different heights and stiffness's (4 conditions) at a controlled velocity and self-selected velocity. If able, they will walk without their AFO at a self-selected pace. Participants will be asked to provide information regarding their health condition and opinions of the conditions tested.

GROUP 1 Patient Inclusion criteria

• Ages: 18-70
• Daily AFO use to address unilateral, below knee functional deficits that result from limb injury or musculoskeletal disease (e.g. fracture, muscle and/or nerve injury, ankle arthritis)
• Greater than 2 weeks using their current AFO
• Ability to walk 50 feet without use of an assistive device (Cane, crutch, etc.)
• Ability to walk at a slow to moderate pace
• AFO fits into traditional footwear
• Able to read and write in English and provide written informed consent

GROUP 1 Patient Exclusion criteria

• Pain > 6/10 while walking during testing or an increase in pain during testing of > 2/10.
• Central Nervous System disorder or disease (e.g. Stroke, Cerebral Palsy, Spinal Cord Injury, or other conditions that result in lower limb spasticity).
• Disorder or disease that affects peripheral nerve function (e.g. diabetes, Charcot Marie Tooth).
• Limited contralateral lower limb function due to injury or neurological/musculoskeletal disorder.
• Use of a hinged/articulating AFO (e.g. Plantar flexion stop, Dorsiflexion assist/stop, free motion), Charcot Restraint Orthotic Walker (CROW) boot, AFOs that restrict all motion in the ankle and foot.
• Use of an AFO that crosses the knee (Knee brace)
• Insufficient space in shoe to accommodate the tallest heel wedge and their AFO
• Visual or hearing impairments that limit walking ability or could limit the ability to comply with instructions given during testing
• Pregnancy - Per participant self-report. Due the expected small number of pregnant individuals, and resulting inability to account for its effect on resulting outcomes participants will be withdrawn from the study.
• Body Mass index > 40.

GROUP 2 Patient Inclusion Criteria

• Ages: 18-70
• Daily AFO use to address below knee functional deficits that result from disease involving the peripheral nervous system (e.g. Charcot Marie Tooth, Multiple Sclerosis, diabetes)
• Greater than 2 weeks using their current AFO (unilateral or bilateral)
• Ability to walk 50 feet without use of an assistive device (Cane, crutch, etc.)
• AFO fits into traditional footwear
• Ability to walk at a slow to moderate pace
• Able to read and write in English and provide written informed consent

GROUP 2 Patient Exclusion Criteria

• Pain > 6/10 while walking or an increase in pain during testing of > 2/10
• Central Nervous System disorder or disease (e.g. Stroke, Cerebral Palsy, Spinal Cord Injury, or other conditions that result in lower limb spasticity)
• Limited function due to limb injury (e.g. fracture, muscle and/or nerve injury)
• Use of a hinged/articulating AFO (e.g. Plantar flexion stop, Dorsiflexion assist/stop, free motion), Charcot Restraint Orthotic Walker (CROW) boot, AFOs that restrict all motion in the ankle and foot.
• Use of an AFO that crosses the knee (Knee brace)
• Insufficient space in shoe to accommodate the tallest heel wedge and their AFO
• Visual or hearing impairment that limit walking ability or limit the ability to comply with instructions given during testing
• Pregnancy - Per participant self-report. Due the expected small number of pregnant individuals, and resulting inability to account for its effect on resulting outcomes participants will be withdrawn from the study
• Body Mass index > 40.

Participants will be blinded to the heel wedge conditions.