Chapter 74 - Gait Analysis

Question 1

Define Kinetic gait analysis and kinematic gait analysis:

Answer 1

Kinetic gait analysis: Measurement of forces acting on the limb during motion (ground reactive forces)
Kinematic gait analysis: Description of the movement of the body in space (ROM, angular velocity, displacement, duration)

Question 2

Which gaits are symmetric and asymmetric?

Answer 2

-Symmetrical: walk, trot, pace
Asymmetrical: Canter, transverse gallop, rotary gallop

Question 3

What are the 2 main phases of the gait cycle?

Answer 3

Stance phase (foot in contact with ground)
- Breaking (put foot down)
- Propulsion (pushing off to lift)
Swing phase (limb in air)

Question 4

What is the ground reaction force?

Answer 4

Forces on the limb in stance phase (Newton’s 3rd law / equal and opposite reactions)
The resultant force of all local forces acting on the foot/paw

Question 5

What are the 9 quantities calculated for each foot fall on a force plate?
Which are most commonly used for analysis in dogs?

Answer 5

Three orthogonal components
- Fx, Fy, Fz - describes the direction of the force

Three spatial components
- x, y, z - describes the location of the force on the plate

Three orthogonal moments
- Mx, My, Mz

The direction of force is most commonly described, Fx (mediolateral), Fy (craniocaudal), Fz (vertical) with the vertical force Fz being most common

Question 6

How do you calculate weight?

Answer 6

Weight = mass(kg) x acceleration of gravity on earth (9.81m/s^2)

Question 7

What do the vertical force Fz and the craniocaudal force Fy represent?

Answer 7

Fz represents the vertical force of the leg and can be used to assess peak vertical force. Creates a bell shaped curve at a trot, M-shaped at a walk

Fy represents braking (positive value) and propulsion (negative value)

Question 8

What is the impulse value?

Answer 8

The area under the force-time curve and takes both force, and contact time into consideration

Question 9

What change is expected regarding peak vertical force and impulse value with pain or lameness?

Answer 9

Both are reduced

Question 10

What is represented by the rising and falling slope of a force-time curve?
What changes are expected with pain/lameness?

Answer 10

• Rising slope depicts the loading rate of the limb and falling slope depects the offloading rate of a limb.

Pain/lameness:
- RIsing slope is reduced (less steep, slower to load limb)
- Falling slope is increased (more steep, fast offloading)

Question 11

How many photocells are required to measure velocity and acceleration?

Answer 11

• Velocity - at least 2 photocells
• Acceleration - At least three photocells

Placed 0.5m above gait platform, 0.5 - 3m apart

Question 12

How do you calculate velocity?

Answer 12

Distance traveled (m) / time (change in time) in seconds

Question 13

How do you calculate acceleration?

Answer 13

Change in velocity (m/s) /time (s)

Question 14

What are some of the main differences of pressure walkways as appossed to force plate?

Answer 14

• Force plates calculate a direct force in three directions whereas pressure walkway only calculates pressure in a vertical direction
• Pressure walkways can record info for each individual limb, force plate only does one limb at a time

Cannot compare one to the other

Question 15

During a trot, what is the average peak vertical force (in % body weight) of the thoracic limb and pelvic limb?

Answer 15

• Thoracic limb 115% BW
• Pelvic limb 72% BW

Question 16

Which gait is the more sensitive and accurate for the detection of low-grade or mild lameness in dogs?

Answer 16

Trot - no overlap of footfalls

Question 17

What is the symmetry index?

Answer 17

The use of an animals own limbs to serve as an internal control for comparison

Question 18

What is a normal level of asymmetry?

Answer 18

Has been reported as less than 3.2 at trot or less than 6%

Question 19

What are some common sources of variability?

Answer 19

• Handler
• Trial repetition
• Habituation
• Changes in velocity, stance time or acceleration/deceleration

Question 20

What are the three joint rotations and the three joint translations in kinematic analysis?

Answer 20

Rotations:
- Flexion and extension
- Internal and external rotation
- Abduction and adduction

Translations:
- Mediolateral
- Proximodistal “joint distraction”
- Craniocaudal “drawer”

Question 21

What is parallax error and perspective error?

Answer 21

• Parallax error: subject moves away from the optical axis of the camera
• Perspective error: When subject moves out of calibrated plane of motion

Question 22

What are the 2 forms of markers that can be used for kinematic analysis?

Answer 22

• Passive markers: Circular/spherical, non-reflective markers
• Active markers: Light-emitting diodes.

Question 23

What point values are commonly assessed using kinematic analysis?

Answer 23

• Range of motion
• Maximal flexion or extension

Question 24

List (3) forms of complete waveform analysis of kinematic analysis:

Answer 24

• Fouriers analysis: can determine whether 2 gait cycles are similar. Deconstructs waveform into its component parts
• Wavelet analysis
• Generalised indicator function analysis - determines where in gait cycle the differences are occuring

Question 25

Define forward dynamics and inverse dynamics:

Answer 25

- Forward dynamics: The process of using forces and moments to directly calculate the resulting motion of an object - Inverse dynamics: The use of available kinetic and kinematic data for the indirect calculation of forces and moments

Question 26

Define joint moment and joint power as it relates to dynamics:

Answer 26

- Joint moment - net joint torque acting around a joint - Joint power - measure of mechanical energy generation and absorption across the joint

Question 27

What are the three orthogonal force components measured during kinetic gait analysis?

Answer 27

Vertical (Fz), craniocaudal (Fy), and mediolateral (Fx) forces.

Question 28

What does peak vertical force (PVF) represent in gait analysis?

Answer 28

The maximum vertical load borne by a limb during stance phase.

Question 29

What is vertical impulse in gait analysis?

Answer 29

The area under the vertical force–time curve during stance phase.

Question 30

Why is trotting preferred over walking for detecting subtle lameness?

Answer 30

Trotting increases limb loading symmetry sensitivity and exaggerates asymmetry.

Question 31

What is the typical static weight distribution in dogs?

Answer 31

Approximately 60% forelimbs and 40% hindlimbs.

Question 32

Why can dynamic peak vertical forces exceed 100% body weight?

Answer 32

Because acceleration and deceleration add inertial forces to body weight.

Question 33

What biomechanical event occurs during the braking phase of stance?

Answer 33

Negative craniocaudal force as the limb decelerates the body.

Question 34

What does symmetry index quantify in gait analysis?

Answer 34

The percentage difference in force parameters between paired limbs.

Question 35

What symmetry index range is generally considered normal in dogs?

Answer 35

Less than approximately 3–6% difference between limbs.

Question 36

Why must velocity be controlled during gait analysis?

Answer 36

Changes in velocity significantly alter ground reaction forces.

Question 37

What is the primary limitation of pressure-sensitive walkways?

Answer 37

They measure only vertical forces and not shear components.

Question 38

How does parallax error affect 2D kinematic analysis?

Answer 38

It distorts joint angle measurement when the limb moves out of the camera plane.

Question 39

What is inverse dynamics in gait analysis?

Answer 39

A computational method using kinematics and ground reaction forces to estimate joint moments.

Question 40

Why is normalization to body weight necessary in kinetic studies?

Answer 40

To allow comparison across individuals of different sizes.

Question 41

What biomechanical change is commonly seen in dogs with cranial cruciate ligament rupture?

Answer 41

Reduced peak vertical force in the affected hind limb.

Question 42

What is the significance of rising slope versus falling slope on force plate data?

Answer 42

Incline alters limb loading and joint moment distribution.

Question 43

What does Fourier analysis evaluate in gait assessment?

Answer 43

The harmonic components of gait waveform patterns.

Question 44

Why can skin motion artifact affect kinematic studies?

Answer 44

Markers placed on skin may not accurately reflect underlying bone motion.

Question 45

What parameter best reflects limb loading over time rather than at a single instant?

Answer 45

Impulse.

Question 46

Why is stance phase duration important in lameness evaluation?

Answer 46

Shortened stance phase often indicates pain avoidance.