Gait Kinematics & Kinetics

Kinematics

Position, velocity and acceleration of a segment, a joint or whole body without regard to the forces causing the movement

- anterior/posterior

- medial/lateral

- vertical

COM moves in what 3 directions during gait?

side

5 cm

Vertical COM movement during gait is best viewed from the _____, and moves about ____cm in adults during mid stance

front/back

4cm

Medial/lateral COM movement during gait is best viewed from the ______ and moves about ____cm in adults during mid stance

Energy conservation

What is COM movement important for during gait?

double limb support

5% and 55%

The minimum vertical COM height occurs at the midpoints of both periods of __________ and is ___% and ___% of the gait cycle

single leg support

30% and 80%

The maximum vertical COM height occurs at the midpoint of both periods of ________ and is ___% and ___% of the gait cycle

midstance

30%

80%

Maximum Medial Lateral COM movement occurs during gait in _____ and occurs at ___% of the gait cycle for one leg & ___% of the gait cycle for the other leg

1) Pelvic rotation

2) Pelvic tilt

3) Knee flexion in stance

4) Ankle Mechanism

5) Foot Mechanism

6) Lateral displacement of the body

6 Determinants of Gait

Determinants of gait

Classical biomechanical factors that minimize the vertical and lateral displacement of the center of mass (COM) during walking, enhancing energy efficiency

lengthens the stride and reduces the downward displacement of the COM and medial lateral displacement

How do pelvic rotations contribute to the determinants of gait to enhance energy efficiency?

Prevents excessive rise of the COM

How does pelvic tilt contribute to the determinants of gait to enhance energy efficiency?

minimizes the peak of the vertical COM displacement (up to 20 deg of flexion in stance)

How does knee flexion in stance contribute to the determinants of gait to enhance energy efficiency?

smooths the path of the COM and reduces energy loss

How does foot and ankle mechanisms contribute to the determinants of gait to enhance energy efficiency?

keeps the COM over the base of support and maintains balance

How does lateral displacement of the body contribute to the determinants of gait to enhance energy efficiency?

- COM is critical for efficient energy expenditure during gait

- Changes energy back & forth from potential energy to kinetic energy

Why is the COM important for gait?

ground reaction force (GRF)

• The body needs to control the GRF by activating muscles to allow for gait

COM determines where the ___________ is applied to a joint

Pelvic obliquity

One side of the pelvis is higher than the other when viewed in the frontal plane

Important for maintaining balance and minimizing energy expenditure during gait

How does the trunk contribute to gait?

7

10%

Trunk rotation (during gait) is about __ degrees. There is restriction of trunk motion that may increase energy expenditure by __%

Geriatric

LBP

Late pregnancy

What populations tend to have less trunk rotation during gait?

GRF is anterior to the knee

If someone is leaning forward, where is the line of GRF?

the knee will extend

What action occurs at the knee if someone is leaning forward and GRF is anterior to the knee?

Used mostly for maintenance of balance

What is shoulder swing primarily used for during gait?

Movement is small: about 2 to 4 degrees of motion

How much does the pelvis move in the sagittal plane (anterior/posterior pelvic tilt) during gait

At right heel contact, pelvis is neutral

What is the orientation of the pelvis at initial contact

Moves into anterior tilt/rotation at midstance

What is the orientation of the pelvis in midstance

Back to anterior tilt/rotation at midswing

What is the orientation of the pelvis at mid-swing

Helps advance the limb

Why does the pelvis move back to anterior tilt/rotation at mid swing

posterior tilt

Pelvis: Sagittal Plane orientation in double limb support =

anterior tilt

Pelvis: Sagittal Plane orientation in single limb support =

Helps increase functional step length

Why might pelvis motion increase with velocity?

anterior

lordosis

Patients with big hip flexion contractures show an exaggerated _____ pelvis tilt and ____ during the second half of stance

Both active and passive forces

What causes pelvic tilt during gait?

To minimize movement of the center of mass (COM)

What is the primary goal of kinematic strategies to minimize energy expenditure during gait?

It is out of phase with the hip (opposite arm and leg move together)

How does shoulder motion relate to hip motion during gait?

arm swing will increase

What happens to arm swing as walking speed increases?

Anterior and posterior pelvic tilt/rotation

What sagittal plane movements occur at the pelvis during gait?

It goes into slight posterior tilt/rotation

What happens to pelvic orientation at ~10% of the gait cycle (double limb support)?

It continues moving into posterior tilt/rotation until toe-off

What happens to the pelvis from 10% of the gait cycle until toe-off?

The iliac crests (watch them rise and fall)

What anatomical landmarks should you watch in frontal plane pelvic observation?

30

Hip is flexed about ___ degrees at initial contact

toe off

During gait, maximum hip extension occurs right before _____

10 degrees

Degrees of max hip extension during gait

in terminal stance, pre-swing, and early swing

When during gait does hip extension occur?

- Weightbearing/stability

- shock absorption

- forward progression

What are the functions of the hip during gait?

Hip flexion

What is the sagittal plane orientation of the hip as it moves into pre-swing

Hip is neutral

What is the sagittal plane orientation of the hip at toe off?

just before initial contact

When during gait does maximal hip flexion occur

about 35 degrees

What is the maximal hip flexion that occurs during gait?

Hip is neutral at initial contact

What is frontal plane orientation of the hip during initial contact

As weight goes on the stance foot

When during gait cycle does hip adduction occur?

5

20%

Max hip adduction is about __ degrees around __% of the gait cycle

at toe-off

When is maximum hip abduction achieved during gait?

5 degrees of hip abduction

What is the maximum hip abduction degree that occurs during gait?

neutral

What is the frontal plane orientation of the hip at initial contact

external rotation

At right initial contact, the right hip is in slight ____

at 50% of the gait cycle

When does max hip IR occur during gait?

mid swing

Max hip ER occurs during ______

5-10 degrees

What is maximum hip internal rotation during gait?

5-10 degrees ER

What is maximum hip external rotation during gait?

knee is flexed about 5 degrees

What is the sagittal plane orientation of the knee at initial contact

about 20 degrees of knee flexion

What is the sagittal plane orientation of the knee at 20% of the gait cycle

stance

During initial contact of the gait cycle, the knee serves as a shock absorber as the body weight is shifted towards the _____ limb

20-60 degrees of flexion for gait

How much knee flexion is needed for gait?

flexing

toe-off

As it gets ready for toe off, the knee starts _____ to get the leg cleared for ______

at initial swing (about 60 degrees of flexion)

When during the gait cycle does maximum knee flexion occur

60 degrees

What is the approximate maximal knee flexion that occurs during gait

Knee moves to a little short of neutral extension in prep for initial contact

What is the orientation of the knee just before initial contact?

The foot plantarflexes to get the foot flat on the ground at 8% of the gait cycle

What is the sagittal plane orientation of the ankle as the foot moves into loading response

Between 5 and 10 degrees of plantarflexion

What is the sagittal plane orientation of the ankle during loading response

about 20 degrees of plantar flexion which occurs at toe off

What is maximal plantarflexion and when during the gait cycle does it occur

dorsiflexes

Orientation of the ankle during swing phase

• During swing, the ankle _____ to about neutral at mid swing to clear the ground

usually under 1cm

What is the typical toe clearance during gait?

in a few degrees of plantarflexion

What is the orientation of the ankle during initial contact?

The first rocker = heel rocker

What is the first rocker mechanism of the foot and ankle

The second rocker = ankle rocker

What is the second rocker of the foot and ankle rocker mechanism work

- The arc of the ankle rocker advances the tibia over the stationary foot

- Preserves momentum

What is the function of the second rocker the ankle rocker of the foot and ankle rocker mechanism work

The third rocker = forefoot rocker

What is the third rocker of the foot and ankle rocker mechanism work

what is the function of the third rocker the forefoot rocker of the foot and ankle rocker mechanism work

- During terminal stance, the heel rises, and the phalanx extend

- The metatarsal heads serve as an axis of rotation for body weight advancement

what is needed for the forefoot rocker to occur

Need 60 deg of first toe extension to accomplish the third rocker

Pronation =

eversion, abduction, & dorsiflexion

Supination =

inversion, adduction, & plantarflexion

Subtalar Joint & Gait

- At initial contact, the heel is in slight inversion (3 degrees)

- Rapid eversion occurs until midstance (30% of the gait cycle)

- Inversion then occurs until toe off

what is maximum eversion that occurs during gait

Max of 2 degrees

what is maximum inversion that occurs during gait

Max of 6 degrees

what is the function of the Rapid eversion that occurs until midstance (30% of the gait cycle)

Absorbs the force of loading the leg

what is the function of the inversion that occurs until toe off

Makes the foot rigid for push-off

what are the key points about Subtalar Joint & Gait supination and pronation

- Moving from supination to pronation allows force absorption during initial contact

- Moving from pronation to supination during pre-swing/toe off helps with push off

In addition to joint angle movements, kinematics also encompasses:

- Joint angular velocity (w) = D angle/D time

- Expressed in radians/second

- Joint angular acceleration (a) = D w / D time

- Expressed in radians/second^2

what is kinetics

Study of the forces related to motion

what is the main determinant of gait kinetics

- The gait kinetics are dictated by the GRF

- GRF Determines the muscle activity required for gait

are kinetics observable

no

what are the primary kinetics we are concerned about in gait mechanics

- Ground reaction force

- Foot forces

what is Ground reaction force:

forces applied to the foot by the ground

what is foot force

force applied to the ground by the foot

joint moment =

- sum of all forces acting on a joint

- Also called torque

Moment arm =

shortest distance between the line of action of a force and the axis of rotation

joint power =

- The rate of work performed by controlling muscles

- Equals the product of the net joint moment and the joint angular velocity

- (P = M * w )

what can affect joint power

Power may be too high or low depending on pathology