the gait cycle

THE GAIT CYCLELecture IX

Dr. Amaal Hassan Mohammed Ebrahim

Introduction

The lower limbs are adapted for stabilityrather than range of motion and that stability is achieved at most of the major joints of the lower limb through the use of strong ligaments and tight fitting bony surfaces rather than the expenditure of energy in the form of muscle contraction.

I. FUNCTIONS OF THE LOWER EXTREMITY

Bi-pedalism is the process by which we are able to stand upright and to move about on 2 limbs.

Bi-pedalism imparts three unique functions on the lower limbs. The limbs must

1- bear weight

2- provide a means for locomotion

3- maintain equilibrium.

FUNCTIONS OF THE LOWER EXTREMITY

A- bear weight A - Weight Bearing Properties

1- Support weight of head and torso with minimal expenditure of energy

2- Bony Features Relatively large areas of articulation Close pack fit of articular surfaces of bones involved in the formation

of joints Hip joint

Wide surface areas Knee joint

Weight supporting arches Arches of the foot

3- Ligaments Strong Maintain stable configuration

1- FUNCTIONS OF THE LOWER EXTREMITY

A- Bear weight

B- Center of Gravity

1- Center of mass of body generally falls halfway between iliac crests and in front of second sacral vertebra

2- Position

Posterior to hip joint

Anterior to knee joint

Anterior to ankle joint


A- bear weightC- Stability

1- Position of joints during normal upright standing Due to center of mass of body

2- Can be maintained while bearing weight with minimal expenditure of energy (muscle contraction)

3- Stable position maintained through use of : ligaments close packing of joints

4- Position Hip joint = extension Knee joint = extension Ankle joint = dorsiflexion no ligamentous support Foot = supinated position


II. Locomotion

Position of the Lower Extremity

Weight bearing / Fixed

Motion occurs with foot fixed to ground

Limb is in good position to support weight

Non weight bearing / Free

Foot is not in contact with the ground

Limb is not in a position to support weight


II. Locomotion2- Knee Joint 1. Hip Joint

-Weight bearing - femur moves on tibia -Non weight bearing - tibia moves on femur Types Flexion - Extension Medial rotation - Lateral rotation

-Weight bearing - pelvis moves on femur -Non weight bearing - femur moves on pelvis Types Flexion - Extension Abduction - Adduction Medial rotation - Lateral rotation

4- Foot (Tarsal Joints) 3. Ankle Joint

Pronation - Supination-Weight bearing - tibia and fibula moves on foot -Non weight bearing - foot moves on tibia and fibula Types Dorsiflexion - Plantar flexion

III. The Gait Cycle

Gait is the medical term to describe human locomotion, or the way that we walk. Interestingly, every individual has a unique gait pattern.

The result of a series of rhythmic alternating movement of the legs(arms, and trunk) which creates forward movement of the body.

Prerequisites of Gait

1. Control Inputs

Sensory input provides the central nervous system (CNS) with the information needed to maintain balance

Visual Vestibular Somatosensory The importance and priority

of the different cues are dependant on the type of task, disturbance and/or environmental conditions

Prerequisites of Gait

Maintain the upright position of the head, arms, and trunk against gravity

Control of foot movement for safe ground clearance and gentle heel contact

Gait Cycle

Series of rhythmic, alternative movements of lower limbs, upper limbs with the trunk leading to forward progression of the center of gravity.

The complete cycle start from the time of one foot touch the ground to the time the same foot touch the ground again.

Phases of gait cycle

1- Stance Phase

Initial Contact

Loading Response

Mid Stance

Terminal Stance

Pre-swing

Phases of gait cycle

Swing Phase

Initial Swing

Mid SwingTerminal

Swing

1- Stance phase

Start from Initial contact (Heel strike) to toe off

Nearly represent about 60% gait cycle

2 periods of double stance 10% each -at these times the body's centre of gravity is at its lowest

1- Stance phase

Stance phase Divided into 5 sub-phases:

1. Initial contact .

2. Loading response.

3. Mid-stance.

4. Terminal stance.

5. Pre-swing.

Stance phase

Begins at the instance that one extremity contacts the ground (initial contact- heel strike) and continues as long as some portion of the foot is in contact with the ground

Ends when the reference foot lifts off the ground (toe off)

Stance phase

The weight bearingphase

Provides the stability of the gait

Necessary for accurate swing phase to take place

Initial contact (Heel Strike)

Initial contact

at initial contact, the knee is extended and the ankle is neutral (or slightly plantar flexed)

Normally, the heel contacts the ground first (in patients with pathological gait patterns, the entire foot or the toes contact the ground initially)

1- Initial contact (Heel Strike)

Normal contact of the heel is on the posterior outside of the heel, not the direct back of the heel.

Position of double support: the heel of the leading stance foot and the toes of the other foot both on the ground

This phase continues until the foot is flat on the ground. This constitutes 20 percent of the total gait cycle.

1- Initial contact (Heel Strike)

On the leading stance limb:

the hip is flexed (approximately 30-35o)

The knee is extended

The foot at right angle to the leg

The heel in contact with the floor

2- Loading Response

Loading response corresponds to the gait cycle's first period of double limb support & ends with contralateral toe off , when the opposite extremity leaves the ground.

during loading, knee flexes 15 deg while ankle plantarflexes 15 degrees, which is an energy-conserving mechanism

throughout first phase of stance, hamstrings and ankle dorsiflexors remain active

quadriceps and gluteal muscles act during loading and throughout early midstance to maintain hip and knee stability

www.MiniSun.com

Gait Cycle Measured by the Sensor from Right Foot

3- Mid-stance Phase

The next phase is the mid-stance phase. In this part of the gait cycle which represents 30 percent of the cycle, your body weight passes over your foot as the body comes forward. This is where your foot (in this case the right foot) supports your body weight.

Foot flat on the floor

A stable position

3- Mid-stance Phase The body is carried forward over the stance

limb with the hip extending and the foot gradually placed on the floor

begins with contralateral toe off and ends when the center of gravity is directly over the reference foot

by midstance the knee is extended & ankle is neutral again

the triceps surae acts to control tibial advancement (preventing the tendency for the ankle to dorsi-flex due to body wt and inertia)

3- Mid-stance Phase

This phase ends as your body weight passes forward eventually forcing your heel to rise.

These two phases which represent one half of the total cycle is the part of the gait cycle where you will experience most heel, arch and mid-foot pain.

4- Terminal Stance

Terminal stance: The second half of the single support from 30 to 50% of the gait cycle and is defined as the time from heel rise until the other limb makes contact with the floor. During this phase body weight moves ahead of the forefoot.

The heel is raised as the body moves forward over the stance limb.

The hip is in hyperextension, internal rotation, and adduction

The knee is extended

5- Pre-swing

Pre-swing: The final double support stance period which is defined from the time of initial contact with the contralateral limb to ipsilateral toe-off.

Swing phase

Swing phase is called the non-weight bearing phase

Begins as soon as the big toe of one limb leaves the ground (after toe off), and finishes just prior to heel strike or contact of the same limb.

Swing phase consists of:

1. Initial swing (acceleration)

2. Mid-swing

3. Terminal swing (deceleration)

Swing phase 1- Initial swing (Acceleration)

Initial swing: The initial third of the swing phase from 60 to 73% of the gait cycle as defined from toe-off to when the swing limb foot is opposite the stance limb.

Forward momentum is provided by the ground reaction to the push-off action (when the heel is off the ground but the toes are in strong contact with the ground)

1-Initial swing (Acceleration)

The hip is in flexion and external rotation

Flexion of the knee is necessary for the swinging limb to clear the ground as it moves forward

2- Mid swing

Mid swing: The middle third of the swing phase from 73 to 87% of the gait cycle as defined from the time the swing foot is opposite the stance limb to when the tibia is vertical.

Begins from maximum knee flexion (when the swing limb is under the body) until the swing limb passes the stance limb and the tibia becomes in a vertical position

3- (terminal swing) Deceleration

Terminal swing: The final third of the swing phase from 78 to 100% of the gait cycle as defined from the time when the tibia is vertical to initial contact.

The momentum slows down as the limb moves into the stance phase again

3- (terminal swing) Deceleration

The knee is extending in preparation for heel strike

The hip becomes more flexed.

The foot in neutral position

As the heel touches the ground, the foot moves into plantar flexion (by the controlling action of the dorsiflexors)

Muscle activity during the gait cycle

The movement pattern that we observe in the lower limbs during walking results from the interaction between external forces (joint reaction and ground reaction) and internal forces (produced by muscles and other soft tissue). Knowledge of the ground reaction force is especially helpful to therapists who must understand how muscle activity and timing contributes to stability and propulsion.

The ground reaction force

The ground reaction force is equal in magnitude and opposite in direction to the force that the body exerts on the supporting surface through the foot.

The ground reaction force

Visualizing ground reaction force vectors (GRFV) to understand typical gait patterns DURING LOADING RESPONSE

DURING MIDSTANCE

LOADING RESPONSE

Orientation of ground reaction force vector (GRFV) in sagittal plane Normal GRF is located

posterior to ankle joint

posterior to knee joint

anterior to hip joint

LOADING RESPONSE

During loading response, ground reaction force produces

a plantar flexion moment at the ankle joint

a flexion moment at the knee

a flexion moment at the hip

The body controls these moments with

eccentric activity in the ankle dorsiflexors

eccentric activity in the knee extensors

isometric activity in the hip extensors

MIDSTANCE

MIDSTANCE Orientation of ground reaction force vector (GRFV) in sagittal plane Normal GRF is located

anterior to ankle joint

anterior to knee joint

posterior to hip joint

MIDSTANCE

an extensor moment at the knee

an extensor moment at the hip


eccentric activity in the ankle plantarflexors

passive force which develops in the posterior knee structures as they elongate during knee extension; knee muscle activity is unnecessary.

eccentric activity in the hip flexors

During midstance, ground reaction force produces a dorsiflexor moment at the ankle joint

TERMINAL STANCE



anterior to knee joint


TERMINAL STANCE

During terminal stance, ground reaction force produces a dorsiflexor moment at the ankle joint

an extensor moment at the knee



activity in the ankle plantarflexors. The plantar flexors, which have acted eccentrically through midstance, now act isometrically. The continued advancement of the pelvis and lower extremity now move the tibia anteriorly, which causes the heel to rise at around 35 to 40 percent of the gait cycle.

passive force which develops in the posterior knee structures as they elongate during knee extension; knee muscle activity is unnecessary.

eccentric activity in the hip flexors

PRESWING



posterior to knee joint


PRESWING

During preswing, ground reaction force produces a dorsiflexor moment at the ankle joint

a flexor moment at the knee



activity in the ankle plantarflexors. The plantar flexors' activity becomes concentric as they develop the important "push off" force for propulsion.

PRESWING

little or no muscle activity at the knee. The knee flexors are not necessary to initiate knee flexion as long as the ground reaction force is located posterior to the knee. At faster walking speeds, the rectus femoris acts to control excessive knee flexion. At very slow speeds, the ground reaction force is inadequate to flex the knee, and the hamstrings are active.

continued hip flexor activity; the hip flexors' eccentric terminal stance activity changes to isometric, then concentric activity during preswing and initial swing.

THE GAIT CYCLEDefinition of terms

Gait Cycle: The period of time from one event (usually initial contact) of one foot to following occurrence of the same event with the same foot.

Gait Stride: The distance from initial contact of one foot to the following initial contact of the same foot.

Normalization of the gait cycle: A method used to achieve uniform representation of the gait cycle (or any part of) for the purposes of comparison or averaging data across subjects. Usual method is based on representation of a percentage of the complete cycle or percentage of stance or swing phase.


Stance phase (ST): The period of time when the foot is in contact with the ground.

Swing phase (SW): The period of time when the foot is not in contact with the ground. In those cases where the foot never leaves the ground (foot drag), it can be defined as the phase when all portions of the foot are in forward motion.


Double support (DS): The period of time when both feet are in contact with the ground. This occurs twice in the gait cycle, at the beginning and end of the stance phase.

Single support (SS): The period of time when only one foot is in contact with the ground. In walking, this is equal to the swing phase of the other limb.


Initial contact (IC): The point in the gait cycle when the foot initially makes contact with the ground; this represents the beginning of the stance phase. It is suggested that heel strike not be a term used in clinical gait analysis as in many circumstances initial contact is not made with the heel. Suggestion: Should use foot strike.

Heel contact (HC): When initial contact is made with the heel. Also referred to heel strike.


Terminal contact (TC): The point in the gait cycle when the foot leaves the ground: this represents the end of the stance phase or beginning of the swing phase. Also referred to as foot off. Toe-off should not be used in situations where the toe is not the last part of the foot to leave the ground.


Toe-off (TO): When terminal contact is made with the toe.

Foot flat (FF): The point in time in the stance phase when the foot is plantar grade.

Heel off (HO): The point in the stance phase when the heel leaves the ground.

the gait cycle

Documents

joint weight

weight bearing foot

lower extremity weight

weight bearing tibia

position hip joint

lower limbs

position of joints

extension knee joint