Dynamic Analysis

Question 1

What are the 2 phases in a gait cycle?

Answer 1

Stance phase: 60% of cycle
Swing phase: 40% of cycle

Question 2

What are 5 methods for obtaining kinematics data?

Answer 2

Video: no wires but passive markers, time consuming analysis, 2D, and skin motion
Electro goniometer: simple concept and data collection but no absolute reference frame and skin motion
Electromagnetic: no line of sight required and one marker per segment but potential metal interference, wires and skin motion
Optoelectronic - Passive: no wires but difficult to recognize markers and skin motion
Optoelectronic - Active: known markers but has wires and skin motion

Question 3

How can a coordinate system be defined from 3 points?

Answer 3

Use the 3 points to develop 2 axes, then use cross product to find third axis vector

Question 4

What are the 5 steps for analysis of kinematic data?

Answer 4

1. Filter (via low pass butterworth)
2. Define coordinate system
3. Reconstruct motion data for fixed frame
4. Determine angular motion and translation
5. Differentiate data to get acceleration of centroids and angular acceleration of segments

Question 5

What is a functional change in gait typically associated with?

Answer 5

Adaption due to a condition caused by illness or injury (a response to pain rather than a mechanical change)

Question 6

Why do patients with full PCL substituting designs tend to lean forward?

Answer 6

Replacement of the PCL can lead to a shorter moment arm for the quadriceps, so the patients lean forward to adapt to this higher force by reducing the load on the quads

Question 7

How does Osteoarthritis affect patient’s gait?

Answer 7

Patients frequently alter their gait to reduce loading on the knee joint by reducing their gait speed. This reduces the external extension moment by reducing the use of the internal flexors (hamstrings) which lowers the contact force.