Biomechanics of gait

By:-
Dr. Hari Narayan Saini (PT)
Associate Professor
NIMS College Of Physiotherapy and Occupational Therapy,
NIMS University, Jaipur
 Definition:-

 Rhythmic, cyclic movement of the limbs in relation

to the trunk resulting in forward propulsion of the
body.
Or
 It is a series of rhythmic alternating motion of arms,
legs and trunk that create forward propulsion.
Or
 Walking pattern of a person.
 Normal gait requires

 Normal functioning of musculoskeletal system of

lower limbs and spine.
 Good sensory feedback from proprioceptive
sensation from feet and joints.
 Visual, labrinthine sensory inputs and coordination
add smoothness, rhythm & elegance to the human
gait.
 Gait terminology

 Base of support
 Step length
 Stride length
 Gait cycle
 Cadence
 Walking velocity
 Double limb support
 Single limb support
 Ground reaction force
 Basic gait terms

Base of support:-
 Distance between a person’s feet while standing or
during ambulation.
 Provides balance & stability to maintain erect
posture.
 The larger the BOS the more stable an object will be.
 Normally 2-4 inches from heel to heel.
 Step length

 Linear distance along the line of progression of one

foot travelled during one gait cycle.
 Approximately 15 inches.
 Child- 50 cm
 Adult- 66 cm
 Step duration:- the amount of time spent in
completion of a single step.
 Step duration:-

The amount of time spent in completion of a single

step.
Its measurements is expressed as sec/step.
When there is weakness or pain in an extremity step
duration maybe decreased on the effected side while
increased on the unaffected side.
 Stride length

 Linear distance in the plane of progression between

successive point of foot to floor contact of the same
foot.
 Normally 27-32 inches.
 Child- 101 cm
 Adult- 132 cm
 Gait cycle

 Period of time from one heel strike to next heel strike

of the same limb.
 Cadence

 It is measured as the number of steps/sec or per minute.

 Cadence = number of steps/sec or min.
 Shorter step length will result in increase cadence at a
given velocity.
 If cadence increases the double support time decreases
and vice versa.
 Normal cadence in man = 110 steps/min
 Normal cadence in woman = 116 steps/min.
 Double limb support

 During normal gait, for a moment, two lower

extremities are in simultaneous contact with the
ground.
 During this period, both legs support the body
weight.
 Happens between push off and toe off on same side
and heel strike and foot flat on the contra lateral
side.
 Gait cycle components

A. Stance phase 60% of the gait cycle:- Ipsilateral

foot in contact with the ground.
 It begins when the foot contacts the ground and
ends when the foot lifts off from the ground.
Note- Closed kinetic chain during weight bearing,
allows forces from lower extremity to be transmitted
to ground, producing movement.
 Stance phase

 1.Heel strike- initial contact

 2.Foot flat- loading
 3.Mid stance- single leg
 4.Heel off- terminal
 5.Toe off- pre swing
 Swing phase

B. Swing phase 40% of the gait cycle:- Ipsilateral foot in

the air.
Swing as soon as the toes leave the surface & terminates
when the limb next makes contact with the surface.
Momentum gained at toe-off helps carry leg through the
swing phase.
 1.Acceleration
 2.Mid swing
 3.Deceleration
 Heel strike

 Beginning of stance phase when the heel contacts the

ground.
 Begins with initial contact and ends with foot flat.
 Foot flat

 It occurs immediately following heel strike.

 It is the point at which the foot fully contacts the
floor.
 Mid stance

 It is the point at which the body passes directly over

the supporting extremity.
 Heel off

 The point following mid-stance the heel of the

reference extremity leaves the ground.
 Toe off

 The point following heel off when only the toe off the
reference extremity is in contact with the ground.
 Swing phase

Acceleration phase:-
 It begins once the toe leaves the ground and
continues until mid swing, or the point at which the
swinging extremity is directly under the body.
 Swing phase

Mid swing:-
 It occurs approximately when the reference
extremity passes directly under the body.
 It extends from end of acceleration to the beginning
of deceleration.
 Swing phase

Deceleration:-
 It occurs after mid swing
 When the reference extremity is decelerating in
preparation for heel strike.
 Difference between walking and running

Walking:-
 Always a double support phase, no flight phase.
Running:-
 No double support phase, always flight phase.
 Determinants of gait

 1.Displacement of center of gravity (COG).

 2. Factors responsible for minimizing displacement
of centre of gravity.
 Center of gravity

 It is an imaginary point at which all the weight of the

body is concentrated at a given instant.
 Center of gravity lies 2 inches in front of the second
sacral vertebra.
 Center of gravity follows vertical displacement and
horizontal displacement.
 Biomechanics

Vertical displacement:-
 Rhythmic up and down movement.
 Highest point = mid stance
 Lowest point = Double support
 Average displacement 5 cm
 .

HORIZONTAL DISPLACEMENT :-
 Rhythmic side to side movement
 Lateral limit = Mid stance
 Average displacement 5cm
 Overall displacement

 Sum of vertical and horizontal displacement .

 Figure ‘8’movement of center of gravity as seen from
antero-posterior .
 These displacement require energy “Greater the
displacement more energy is needed”.
 Factors responsible for minimizing the
displacement of center of gravity
 Major determinants
 Pelvic rotation (transverse plane )
 Pelvic lateral tilt (obliquity )
 Knee flexion during stance
 Ankle mechanism (dorsi flexion)
 Ankle mechanism (planter flexion)
 Step width
 Minor determinants

Neck movement
Swinging of arms
 1.Pelvic rotation

 Rotation of pelvis in horizontal plane in swing phase,

total of 8 degree.
Decrease angle of hip flexion and extension
Enables a longer step length without further lowering
of center of gravity.
 2. Pelvic tilt

 The pelvis slopes downwards laterally towards the

leg which is in swing phase.
 Reduces the vertical movements of the upper body
and thereby increase energy efficiency.
 Decrease the displacement of center of gravity.
 3. Knee flexion in stance

 As the hip joint passes over the foot during the

support phase, there is some flexion of the knee. This
reduces vertical movements at the hip.
 Decrease the displacement of centre of gravity.
 4. Ankle mechanism

 Lengthen the leg at heel strike.

 Reduce the lowering of centre of gravity, hence
smoothen the curve of gravity.
 5. Foot mechanism

 Lengthen the leg at toe off as ankle moves from

dorsiflexion to planter flexion.
 Reduce the lowering of centre of gravity, hence
smoothen the curve of gravity.
 Trunk and arms

 The trunk, arms and shoulders also rotate to ensure

balance.
 Upper limb swings opposite to stance leg to produce
a smooth balance gait.
 6. Lateral displacement of body

 In normal gait, width of walking base is narrow, decrease

the lateral displacement of centre of gravity.
 Decrease muscular energy consumption due to decrease
lateral acceleration and deceleration.
 Due to complex interaction of muscular activity and
joints motion in lower limb centre of gravity follows a
smooth sinusoidal curve.
 It reduce the significant energy consumption of
ambulation.
 Gait in children (<2 years)

 Gait of small children differs from that of adult

 The walking base is wider.
 The stride length and speed are lower and the cycle time shorter (
higher cadence ).
 Small children have no heel strike, initial contact being made
shorter ( higher cadence).
 Small children have no heel strike, initial contact being made by flat
foot.
 There is very little stance phase and knee flexion.
 The whole leg is externally rotated during the swing phase.
 There is an absence of reciprocal arm swinging.
 Gait in elderly

 The age related changes in gait takes place in decade

after 70 yrs.
 There is a decreased stride length, increased cycle time
(decreased cadence).
 Relative increase in duration of stance phase of gait time
(decrease cadence).
 The speed almost always reduced in elderly people.
 Reduction in total range of hip flexion and extension.
 Reduction in swing phase and knee flexion.
 Function of the determinants of gait

 Increase the efficiency and smoothness of gait.

 Decrease the vertical and lateral displacement of
centre of gravity.
 Decrease the energy expenditure.
 Make gait more graceful.
 Kinematic gait analysis

 Describe the movement pattern without regard for

the force involved in producing the movement.
 Kinetic gait analysis
 Determine the force that are involved in the gait.
 Gait analysis

 Observational method- naked eye examination

 Photographic method- television, video, movie analysis
 Force plate study method- ground reaction force method
 Electromyographic study (EMG).
 Electro goniometric study- it is used to study the joints
during gait.
 Energy expenditure/requirement method
 Multichannel functional electrical stimulation method
(MFES).
 Clinical gait analysis

A. Observational gait data: Qualitative

Clinician watches patients walk
Advantages:-
-Require little or no instrumentation
-Inexpensive
-Yield general description of gait variables.
 Clinical gait analysis

B. Gait parameters: Quantitative

 The gait parameter measurement are made by timing
progress over a 16 m walkway and identifying events by
means of foot switch system.
 These instrument identify the part contacting the ground
with data transmitted by telemetry.
 Photographic methods are most accurate.
 After film development, each frame is analysed using
vanguard motion analyser and sonic digitizer.
 Pathological gait

 Scissoring gait Knock knee gait

 In toeing gait Genu recurvatum gait
 Out toeing gait Short limb gait
 High stepping gait Quadricep gait
 Circumduction gait Gluteal medius gait
 Waddling gait Gluteal maximus gait
 Trendelenberg gait Stiff hip gait
 Drunkers gait Antalgic gait
 Festinant gait
 Antalgic gait

 Gait pattern in which stance phase on affected side is

shortened due to pain in the weight bearing limb, at
knee, hip, foot pain.
 There is corresponding increase in stance phase on
unaffected side.
 Common causes- OA, fractures, tendinitis.
 Trendelenberg gait

 Any condition which disrupts the osseo-muscular

mechanism between pelvis and femur.
 Weak abductors(power), acetabulo-femoral articulation
defect (fulcrum), defective lever system causes
Trendelenberg gait .
 Here the abductor action in pulling the pelvis downwards
in stance phase become ineffective and the pelvis drops
on the opposite side causing instability.
 To prevent this body lurches on the same side.
 .
 Usually unilateral.
 If bilateral = waddling gait
 Causes- A. Weak abductors:- poliomyelitis, muscular
dystrophies, motor neuron disease.
B. Defective fulcrum:- congenital dislocation of hip,
pathological dislocation of hip.
C. Defective lever:- fracture neck of femur, perthes
disease, coxa vera.
 Circumduction gait

 In hemiplegic patients.
 To avoid the foot from scrapping the ground, the hip
and the lower limb rotates outward.
 High stepping gait

 Due to foot drop.

 On attempt of heel strike, the toe drops to the
ground first.
 To avoid this the patient flexes the hip and knee
extensively to raise the foot and slaps it on the floor
forcibly.
 Scissoring gait

 Here one leg crosses directly over the other leg with
each step due to adductor tightness.
 Seen in cerebral palsy.
 Drunkers or reeling gait

 Patient tends to walk irregularly on wide base,

swinging sideways without stability and balance.
 Caused due to cerebellar lesion.
 With unilateral lesion of cerebellum, balance is lost
towards the side of the lesion.
 Genu recurvatum gait

 In paralysis of hamstring muscles the knee goes in

for hyper extension while transmitting the weight in
mid stance phase.
 Seen in poliomyelitis.
 Short leg gait

 Shortening less than 1.5 cm compensated by pelvic

tilt, and shortening up-to 5 cm compensated by
equinus.
 Shortening more than 5 cm the patient dips his body
on that side.
 Festinant gait

 Seen in Parkinson’s disease.

 Steps are short that the feet barely clears the ground.
 Quadriceps gait

 Normally the knee locked by the quadriceps

contraction while transmitting weight to the lower
limb during midstance.
 Hence patient with weak quadriceps stabilizes his
knee by learning forward on the affected side and
pressing over lower thigh by his ipsilateral hand or
fingers.
 Gluteus maximus gait(Backward lurch)

 Due to weakness in gluteus maximus muscle, while

the body peoples forward during midstance phase,
trunk is lurched posterior to effect posterior pelvic
and shifting the centre of gravity towards stance hip.
 Seen in polio myeilitis and above knee amputation
with prosthesis.
 Stiff hip gait

 When the hip is ankylosed, it is not possible to flex at

the hip joint during walking to clear the ground in
the swing phase.
 Hence the person with stiff hip, lifts the pelvis on
that side and swings the leg with the pelvis in
circumduction and moves it forward.
 Stamping/Ataxic gait

 It occurs in sensory ataxia in which there is loss of

sensation in lower extremity due to disease processes in
peripheral nerves, dorsal roots, dorsal column of spinal
cord.
 Due to absence of deep position sense, the patient
constantly observes placing of his feet.
 Hip is hyper flexed and externally rotated & forefoot is
dorsiflexed to strike ground with a stamp.
 Seen in peripheral neuritis and brain stem lesion in
children, tabes dorsalis in adults.
 Alderman’s gait

 Seen in tuberculosis of spine in lower dorsal and

upper lumbar vertebra.
 Patient walk with head and chest thrown backward
and protuberant abdomen and legs thrown wide
apart.
.
 In-toeing gait

 In-toeing means that when a child walks or runs, the feet turn
inward instead of pointing straight ahead. It is commonly
referred to as being pigeon toed.

 In-toeing is often first noticed by parents when a baby begins

walking, but children at various ages may display in-toeing for
different reasons. Three conditions can cause in-toeing:-
Metatarsus adductus (the foot turns inward).
Tibial torsion (the shinbone turns inward).
Femoral anteversion (the thighbone turns inward).
 Out toeing gait

 Out toeing is a condition that can occur in children

in in which the toes point outward rather than
straight ahead.
 In many cases, it doesn’t cause any problems in
toddlers and corrects itself as the child grows. Other
cases of out toeing can be tied to more serious
conditions and may require medical attention.
 Gait training

 Aim:- To achieve safe, easy, effortless normal gait

pattern.
Non ambulatory phase
 1.Asses and improve the range of movement
 2.Treat contractures
 3.Improve the cardio respiratory status
 4.Shadow walking.
 Ambulatory phase
 Support by orthotic and prosthesis
 Parallel bar walking
 Encourage reciprocal arm swinging
 Follow other forms of walking :-
Turning
Side walk
Back walk
Squatting
Getting up
Walking on uneven rough surface.
 Crutches

 Crutches are a type of walking aid that serve to increase

the size of an individual's base of support.
 They transfer weight from the legs to the upper body and
are often used by people who cannot use their legs to
support their weight (from short-term injuries to lifelong
disabilities).
.
 Crutch Type

 There are three types of crutches:-

Axillary crutch
Elbow crutch
Gutter crutch
 Axillary or underarm crutches :-

 They should be positioned with 2 fingers of distance

between the axilla and the axilla pad with the elbow
flexed between 20-30 degrees.
 The design includes an axilla bar, a handpiece and double
uprights joined distally by a single leg.
 They are adjustable in height; both the overall height and
handgrip height can be adjusted.
 Forearm crutches

 Forearm crutches: (or lofstrand, elbow or Canadian

crutches).
 Their design includes a single upright, a forearm cuff and
a handgrip.
 The height of forearm crutches is indicated from handgrip
to the floor (adjustable from 29 to 35 inches / 74 to 89
cm).
 Gutter Crutches

Gutter Crutches: (or adjustable arthritic crutches, forearm

support crutches)-
 An additional type of crutch, which is composed of a
padded forearm support, made up of metal, a strap and
adjustable handpiece with a rubber tip.
 These crutches are used for patients who are partial
weight bearing, and are particularly useful for clients with
rheumatoid conditions.
 Walking Pattern

There are several different walking patterns an individual using

crutches may adopt, including:-
Two-point crutch gait:- In two-point crutch gait, the crutches and the
non-weight bearing / affected limb (due to fracture, amputation, joint
replacement etc) make up one point and the uninvolved leg makes up
the other point.
• The crutches and affected limb are advanced as one unit, and the
uninvolved weight-bearing limb is brought forward to the crutches as
the second unit.
• This gait pattern is less stable as only two points are in contact with
floor. Thus, good balance is needed to achieve two-point crutch gait.
 Two-point gait:-

 The right foot and left crutch are advanced

simultaneously, followed by the left foot and right crutch.
There are two points in contact with the floor at any one
time!
 Running gait

 Running gait is similar to walking in terms of locomotor

activity.
 Running requires:-
Greater balance- double float period
Muscle strength
Joint ROM- absorb increased energy to control weight
during running gait cycle, the GRF and COP increase to
250% of body weight (double that of walking).
 Difference between running and walking

 Time and ground contact pattern.

 Greater joint motion and eccentric muscle work.
 Double and single limb support (period of double limb
float).
<40% of stance and >60% swing (vice versa)
 Time spends in float leads to increase in running speed.
 This phase starts from ipsilateral toe off.
 Gait cycle of running

 Gait cycle begins when one foot comes in contact

with the ground and ends when the same foot
contacts the ground again.
 2 phases-
1. Stance- Loading (heel strike to foot flat)
Mid stance (foot flat to heel off)
Propulsion (heel off to toe off)
 2. swing phase-

 Initial swing
 Terminal swing
Forward descent
 Kinetics of running

 Ankle, knee, hip power patterns are similar in

running to those of walking, only the velocity
influences the amplitude.
 When forward speed of runner increases, the peak
GRF and rate of loading increases.
 During running sharp GRF at initial contact
resulting in an impact peak (depends on foot strike
pattern).
 Cont.

 After initial peak GRF reaches 2.2 to 2.6 times of

body weight in runners.
 During mid stance GRFs are highest on body.
 Anteroposterior GRF can alter through strike style
(fore foot and heel), cadence and running surface
(downhill and uphill).
 Kinematics of running

 Sagittal plane- in this plane running exhibit out

pelvic tilt and thigh angle.
 At initial contact- hip flexes 20-45 degree after which
it goes for extension till toe off.
 At terminal swing hip flexion decreases that lead to
reduction of velocity of the foot relative to the
ground.
 In runners pelvic motion is minimised
 .

 Increase lumbar lordosis.

 At initial contact knee flexes 15-25 degree.
 At mid stance knee flexes 45 degree
 At propulsion phase knee extends of 25 degree
 But in swing phase knee reaches beyond 90 degree of
flexion.
 At initial contact ankle in neutral.
 .

 At mid stance 20 degree of dorsi flexion as leg is loaded.

 At toe off 15-35 degree of planter flexion and that
continues till preparation of heel strike.
 At initial contact foot goes for supination followed by
calcaneous inversion
 As the progression occurs subtalar joints pronates
followed by hind foot eversion and tibial internal
rotation.
 Frontal plane

 In this plane hip is adducted 6-12 degree with

respect to pelvis from initial contact to midstance.
 Transverse plane

 Movement pattern in this plane important for energy

efficiency.
 At initial contact – pelvis exhibit 8 degree of forward
rotation.
 Hip external rotation of 10 degree (mid stance-toe
off)
 Foot shows max external rotation in midswing of 15
degree.