Stepping through Science

Question 1

The gait cycle overview

Answer 1

• Consists of stance and swing phase
• two double support phases and two single support phases

Question 2

Stride vs step

Answer 2

• Stride is heel strike to same foot heel strike
• step is heel strike to opposite heel strike

Question 3

Stance Subphase

Answer 3

1. Loading Response: Initial contact to opposite toe off
2. Midstance: opposite toe-off to heel raise
3. Terminal stance: heal raise to opposite initial contact
4. Pre-swing: Opposite initial contact to toe-off

Question 4

Swing subphases

Answer 4

1. Initial swing: toe-off to feet adjacent
2. Mid-swing: feet adjacent to tibia vertical
3. Terminal swing: tibia vertical to initial contact

Question 5

Gait and healthy aging

Answer 5

Reductions in
- muscle mass and strength
- motor unit function and number
- endurance (higher metabolic cost)

Changes in the nervous system
- Slow, more variable and asymmetric gait
- Sensory declines (vision and proprioception, spatial awareness)

Question 6

Spatial temporal parameters and their change in age

Answer 6

• Stride length
• Step height
• Cadence
• Speed
• Base of support
• All decrease except BoS widens

Question 7

Sensor based measuring tools

Answer 7

• Force Plates
• Inertia measurement units

Question 8

Camera based measurement tools

Answer 8

• Marker-based motion capture
• Marker-less motion capture

Question 9

Force Plates

Answer 9

• Sensorized boards (piezoelectric - convert electrical signal to force or strain gauge - deformation based)
• Operate based on newtons 3rd law: equal and opposite reaction
• Used to measure GRF

Question 10

GRF through the gait cycle

Answer 10

• Heel Strike: small backwards
• Loading: large backwards
• Midstance: medium up
• Push-off: large forward
• Toe-off: small forward

Question 11

IMUs

Answer 11

• Main circuit board
• 3 sensors (accelerometer, gyroscope, magnetometer)
• 3 dimension axis for each sensor (9 total)
• Operate off Newton’s 1st law (inertia)
• Utilize sensor fusion - combining multiple sensors to get whole picture, allows calculation of joint angles

Question 12

Marker(-less) motion capture

Answer 12

• Utilizes many cameras - require calibration (create point of reference) and may require markers
• Cameras help see video to match data with movements
• Clothing can interfere with data collection
• Software compiles data, digitizes the points in space, estimates joint angles/forces

Question 13

What is knee osteoarthritis

Answer 13

• Non-curable, degenerative joint disease impacting 4 million Canadians
• Most commonly affects medial compartment (takes 60-80% of load)
• Associated with aging abnormal joint loading - injury, obesity

Question 14

Joint changes in knee OA

Answer 14

• Osteophyte formation (bone spurs)
• Degenerating cartilage
• Inflammation surrounding tissues (bursa or meniscus)
• Irritated or damaged articulating surfaces

Question 15

Knee Flexion Angle

Answer 15

1. Knee absorbs impact through slight flexion
2. Knee begins to extend during stance phase
3. Nearing toe-off, knee flexes closer to toe-off
4. Flexion continues through mid-swing
5. knee extension in preparation for heel strike

Question 16

Knee flexion angle in knee OA

Answer 16

• Decrease in overall knee flexion
• Stiff knee gait
• total knee arthroplasty can improve knee flexion

Question 17

Knee Adduction Movement

Answer 17

• force applied to medial side off knee through adduction
• Prozy measure for knee loading
• Increases in KAM indicate: disease progression, increased pain, decreased function

Question 18

Foot progression angle

Answer 18

• Measured relative to the direction of travel (calcaneus to 2nd metatarsal)
• Gait modification for FPA is easy, effective and can be done out of clinic

Question 19

KAM plot in relation to FAP

Answer 19

• KAM higher when toe out during early stance phase
• KAM higher when toe in during late stance phase

Question 20

MOCAP and foot progression angle

Answer 20

• markers on 1st metatarsal, 5th metatarsal, calcaneus
• midpoint between 1st and 5th used to find direction of foot
• several steps taken to determine direction of travel
• direction of travel compared to direction of foot on average to determine foot progression angle