CPO CPO Biomechanics & Gait Analysis 2 — Questions and Answers
Question 1: Which orthotic alignment principle ensures the knee joint center is positioned anterior to the ground reaction force vector during stance to promote stability?
- Dynamic alignment
- Passive knee stability through GRF anterior to joint (Correct answer)
- Active quadriceps recruitment
- Posterior socket trim lines
Correct answer: Passive knee stability through GRF anterior to joint
Positioning the ground reaction force anterior to the knee joint center creates an extension moment, providing passive knee stability without active muscle effort.
Question 2: A transfemoral amputee demonstrates lateral trunk bending toward the prosthetic side during stance. Which prosthetic cause should be investigated first?
- Prosthetic limb too short (Correct answer)
- Prosthetic limb too long
- Excessive socket adduction
- Soft prosthetic foot
Correct answer: Prosthetic limb too short
A prosthetic limb that is functionally too short causes the patient to laterally bend toward that side to maintain balance and clear the floor.
Question 3: What does cadence refer to in clinical gait analysis?
- Distance covered per step
- Number of steps taken per unit time (Correct answer)
- Speed of swing phase
- Ratio of stance to swing time
Correct answer: Number of steps taken per unit time
Cadence is defined as the number of steps (or strides) taken per minute and is a fundamental temporal parameter of gait.
Question 4: During KAFO fitting, which biomechanical factor most influences the decision to set the knee joint in slight flexion rather than full extension?
- Cosmesis preference
- Reducing energy expenditure during ambulation (Correct answer)
- Improving quadriceps function
- Decreasing lumbar lordosis
Correct answer: Reducing energy expenditure during ambulation
A slight knee flexion angle (about 5°) in a KAFO reduces energy expenditure by allowing a more natural gait pattern with smoother weight transfer.
Question 5: Which parameter best describes the symmetry of a prosthetic user's gait and is frequently used to compare stance time between limbs?
- Step width
- Symmetry index (SI) (Correct answer)
- Treadmill velocity
- Pelvic obliquity angle
Correct answer: Symmetry index (SI)
The symmetry index compares values (such as stance time) between limbs and quantifies the degree of asymmetry in prosthetic gait.
Question 6: Which prosthetic foot category is specifically designed to store and return energy during push-off, improving ambulatory efficiency?
- SACH foot
- Single-axis foot
- Energy-storing-and-return (ESAR) foot (Correct answer)
- Multi-axial foot
Correct answer: Energy-storing-and-return (ESAR) foot
Energy-storing-and-return (ESAR) feet use flexible carbon fiber or composite keels that deflect under load and release energy at push-off, reducing metabolic cost.
CPO CPO Biomechanics & Gait Analysis 2
Which orthotic alignment principle ensures the knee joint center is positioned anterior to the ground reaction force vector during stance to promote stability?