ORTHOTIC DEVICES STUDY GUIDE 2026/2027
QUESTIONS AND SOLUTIONS RATED A+
✔✔3-point pressure system - ✔✔Continuous control in all conditions (stance + swing)
using three forces to control a joint moment.
✔✔First-class lever system (orthoses) - ✔✔Orthotic force systems act like a first-class
lever: force-fulcrum-force.
✔✔Effort arm - ✔✔Distance from force application to axis/fulcrum.
✔✔Resistance arm - ✔✔Distance from resistance/segment load to axis/fulcrum.
✔✔Mechanical advantage - ✔✔Improved by longer lever arms; less force required for a
given torque.
✔✔Angle of application - ✔✔Force application angle relative to lever; 90° is optimal for
maximal effect.
✔✔Stress - ✔✔Force per unit area; includes compression, shear, tensile, bending,
torsion.
✔✔Compression stress - ✔✔Forces pushing toward each other.
✔✔Shear stress - ✔✔Forces parallel to a surface.
✔✔Tensile stress - ✔✔Forces pulling away from each other.
✔✔Elastic force - ✔✔Force resulting from stretch; depends on tolerance, healing stage,
chronicity, severity/density of contracture, age, lifestyle.
✔✔Mobilization force (small hand joints) - ✔✔Approx. 100-300 grams.
✔✔Mobilization force (larger structures) - ✔✔Approx. 350+ grams.
✔✔Temporary (prefab) orthosis - ✔✔Off-the-shelf; short-term use, assess benefit,
generic fit, usually less costly.
✔✔Definitive orthosis - ✔✔Custom; used when permanent benefit needed and
condition is stable; more costly.
✔✔AFO - ✔✔Ankle-foot orthosis.
✔✔Static AFO - ✔✔Rigid AFO designs primarily controlling motion (e.g., solid AFO).
, ✔✔Dynamic AFO - ✔✔AFO designs allowing some motion/energy return (e.g.,
articulating, PLS, carbon fiber).
✔✔Solid AFO (SAFO) - ✔✔Holds ankle fixed (immobilizes in 3 planes), typically near
neutral; assists swing clearance, prepositions foot for IC, promotes stance stability.
✔✔SAFO effect on rockers - ✔✔Fundamentally limits function of all 3 ankle rockers.
✔✔Posterior Leaf Spring (PLS) AFO - ✔✔Flexible thermoplastic; trimlines posterior to
malleoli; often set in DF; controls PF at IC→LR, allows DF in stance, supports forefoot
during swing.
✔✔Energy return AFO - ✔✔Carbon fiber AFO designed to store/return energy;
lightweight.
✔✔Articulating (hinged) AFO - ✔✔Mechanical ankle joint allowing PF/DF; requires ~5°
true ankle DF; may include PF stop or DF stop.
✔✔PF stop (hinged AFO) - ✔✔Limits plantarflexion; can help control knee
hyperextension in midstance.
✔✔DF stop (hinged AFO) - ✔✔Limits dorsiflexion; can help control knee flexion in
terminal stance when plantarflexors are weak.
✔✔UCBL - ✔✔Foot orthosis emphasizing rearfoot/midfoot control; used for
pronation/supination control.
✔✔SMO - ✔✔Supramalleolar orthosis for medial-lateral ankle/subtalar control.
✔✔DAFO - ✔✔Dynamic AFO emphasizing flexible control/containment.
✔✔Metal upright AFO - ✔✔AFO with metal uprights/stirrups and mechanical axis; can
include DF/PF assist.
✔✔BICAAL - ✔✔Bichannel adjustable ankle locking mechanism used with metal upright
AFOs.
✔✔Klenzak joint - ✔✔Double-action ankle joint often used in metal upright AFOs.
✔✔Medial T-strap - ✔✔Strap used to improve medial-lateral control (often with metal
upright designs).
QUESTIONS AND SOLUTIONS RATED A+
✔✔3-point pressure system - ✔✔Continuous control in all conditions (stance + swing)
using three forces to control a joint moment.
✔✔First-class lever system (orthoses) - ✔✔Orthotic force systems act like a first-class
lever: force-fulcrum-force.
✔✔Effort arm - ✔✔Distance from force application to axis/fulcrum.
✔✔Resistance arm - ✔✔Distance from resistance/segment load to axis/fulcrum.
✔✔Mechanical advantage - ✔✔Improved by longer lever arms; less force required for a
given torque.
✔✔Angle of application - ✔✔Force application angle relative to lever; 90° is optimal for
maximal effect.
✔✔Stress - ✔✔Force per unit area; includes compression, shear, tensile, bending,
torsion.
✔✔Compression stress - ✔✔Forces pushing toward each other.
✔✔Shear stress - ✔✔Forces parallel to a surface.
✔✔Tensile stress - ✔✔Forces pulling away from each other.
✔✔Elastic force - ✔✔Force resulting from stretch; depends on tolerance, healing stage,
chronicity, severity/density of contracture, age, lifestyle.
✔✔Mobilization force (small hand joints) - ✔✔Approx. 100-300 grams.
✔✔Mobilization force (larger structures) - ✔✔Approx. 350+ grams.
✔✔Temporary (prefab) orthosis - ✔✔Off-the-shelf; short-term use, assess benefit,
generic fit, usually less costly.
✔✔Definitive orthosis - ✔✔Custom; used when permanent benefit needed and
condition is stable; more costly.
✔✔AFO - ✔✔Ankle-foot orthosis.
✔✔Static AFO - ✔✔Rigid AFO designs primarily controlling motion (e.g., solid AFO).
, ✔✔Dynamic AFO - ✔✔AFO designs allowing some motion/energy return (e.g.,
articulating, PLS, carbon fiber).
✔✔Solid AFO (SAFO) - ✔✔Holds ankle fixed (immobilizes in 3 planes), typically near
neutral; assists swing clearance, prepositions foot for IC, promotes stance stability.
✔✔SAFO effect on rockers - ✔✔Fundamentally limits function of all 3 ankle rockers.
✔✔Posterior Leaf Spring (PLS) AFO - ✔✔Flexible thermoplastic; trimlines posterior to
malleoli; often set in DF; controls PF at IC→LR, allows DF in stance, supports forefoot
during swing.
✔✔Energy return AFO - ✔✔Carbon fiber AFO designed to store/return energy;
lightweight.
✔✔Articulating (hinged) AFO - ✔✔Mechanical ankle joint allowing PF/DF; requires ~5°
true ankle DF; may include PF stop or DF stop.
✔✔PF stop (hinged AFO) - ✔✔Limits plantarflexion; can help control knee
hyperextension in midstance.
✔✔DF stop (hinged AFO) - ✔✔Limits dorsiflexion; can help control knee flexion in
terminal stance when plantarflexors are weak.
✔✔UCBL - ✔✔Foot orthosis emphasizing rearfoot/midfoot control; used for
pronation/supination control.
✔✔SMO - ✔✔Supramalleolar orthosis for medial-lateral ankle/subtalar control.
✔✔DAFO - ✔✔Dynamic AFO emphasizing flexible control/containment.
✔✔Metal upright AFO - ✔✔AFO with metal uprights/stirrups and mechanical axis; can
include DF/PF assist.
✔✔BICAAL - ✔✔Bichannel adjustable ankle locking mechanism used with metal upright
AFOs.
✔✔Klenzak joint - ✔✔Double-action ankle joint often used in metal upright AFOs.
✔✔Medial T-strap - ✔✔Strap used to improve medial-lateral control (often with metal
upright designs).
