COF Biomechanics & Gait Analysis 3 — Questions and Answers
Question 1: When prescribing a KAFO for a patient with quadriceps weakness, the primary biomechanical goal is to:
- Prevent excessive ankle dorsiflexion during stance
- Maintain knee extension moment throughout stance phase (Correct answer)
- Reduce ground reaction force at the foot
- Limit subtalar joint pronation
Correct answer: Maintain knee extension moment throughout stance phase
A KAFO for quadriceps weakness aims to provide a knee extension moment during stance, preventing the knee from buckling under body weight.
Question 2: The 'rocker bottom' sole modification on a shoe or AFO primarily functions to:
- Increase ankle dorsiflexion range of motion
- Facilitate forward progression of the center of mass without requiring ankle motion (Correct answer)
- Reduce lateral ankle instability
- Increase medial longitudinal arch support
Correct answer: Facilitate forward progression of the center of mass without requiring ankle motion
A rocker bottom allows the center of mass to advance forward during terminal stance by substituting for ankle plantarflexion/push-off when ankle motion is limited.
Question 3: During observational gait analysis, a patient demonstrates a lateral trunk lean toward the stance limb. This is most commonly associated with:
- Contralateral hip abductor weakness
- Ipsilateral hip abductor weakness (Correct answer)
- Bilateral ankle equinus
- Excessive knee hyperextension
Correct answer: Ipsilateral hip abductor weakness
Lateral trunk lean (Trendelenburg gait) occurs ipsilaterally to compensate for weakness of the hip abductors on the same side as the stance limb.
Question 4: The 'ankle rockers' (heel rocker, ankle rocker, forefoot rocker) described by Perry describe energy-efficient mechanisms during which phase of gait?
- Swing phase only
- Stance phase only (Correct answer)
- Both stance and swing phases equally
- Initial contact only
Correct answer: Stance phase only
Perry's three ankle rockers (heel, ankle, and forefoot) all occur during the stance phase of gait to facilitate smooth forward progression of the body's center of mass.
Question 5: A patient with a complete L3 spinal cord injury would most likely require which type of orthosis for community ambulation?
- Foot orthosis (FO) only
- Ankle-foot orthosis (AFO)
- Knee-ankle-foot orthosis (KAFO) (Correct answer)
- Hip-knee-ankle-foot orthosis (HKAFO)
Correct answer: Knee-ankle-foot orthosis (KAFO)
An L3 complete injury preserves hip flexion and some knee extension but results in absent ankle control and absent knee stability, necessitating KAFO support for functional ambulation.
Question 6: In biomechanical analysis, 'kinetics' refers to the study of:
- Joint angles and segment positions during movement
- Forces and moments that cause or result from movement (Correct answer)
- Electromyographic activity of muscles during gait
- Temporal and spatial parameters of walking
Correct answer: Forces and moments that cause or result from movement
Kinetics is the branch of biomechanics concerned with the forces, moments, and powers that cause or result from movement, as distinguished from kinematics which describes motion.
Question 7: Which gait deviation is most commonly associated with a rigid plantarflexion contracture (equinus deformity) during the loading response?
- Excessive heel strike force
- Absence of heel contact (forefoot or toe strike pattern) (Correct answer)
- Increased knee flexion at initial contact
- Exaggerated hip extension at terminal stance
Correct answer: Absence of heel contact (forefoot or toe strike pattern)
A rigid equinus contracture prevents heel rocker function, causing the patient to contact the ground with the forefoot or toes instead of the heel at initial contact.
COF Biomechanics & Gait Analysis 3
When prescribing a KAFO for a patient with quadriceps weakness, the primary biomechanical goal is to: