Abnormal Gait

Department of Physical TherapyNEW YORK UNIVERSITY

Historical PerspectiveTendency to classify gait according

to disease or injury state Hemiplegic gait Parkinsonian gait Spastic gait Quadra- or paraplegic gait Amputee gait, etc.

RationaleA specific disease or injury state

manifested as a discrete and clinically describable problem with the mechanics of gait

Our Starting PointWe’ll take a deficit-oriented vs.

disease- oriented approach to abnormal gait analysis

Example: “How might a spastic hamstring on one side, secondary to hemiplegia caused by a CVA, affect gait mechanics?”

AnswerA spastic hamstring may limit step or

stride excursion and/or pelvic transverse rotation

Preferred Rate of AmbulationFree or comfortable walking speedSelf-selected paceRate at which the normal individual

is most energy efficientRange: ~2.5 - 4.0 mph (cadence of

~75 - 120 steps per minute)Will vary from individual-to-individual

Walking Rates - Historical PerspectiveHistorically walking rates classified

as: Slow: ~75 - 90 steps per minute Medium: ~90 - 105 steps per minute Fast: ~105 - 120 steps per minute

Energy Cost vs. Rate

Summary & InterpretationOxygen expenditure is least while

walking at a rate somewhere between ~85 to 110 steps per minute irrespective of stride (or step) length

Individuals tend to gravitate toward a self-selected pace which is most energy efficient for that individual

Enter - The Idea of a ‘Preferred Rate’A preferred rate of ambulation is

a self-selected walking pace that an individual assumes that is most energy efficient

Clinical ImplicationSince there is apparently a rate-

dependent issue that drives gait efficiency the PT should understand that going slower than and faster than the preferred rate will lead to inefficiency and potential stress on the cardiovascular and motor control systems

Why is Gait More Efficient at Preferred Rate?What is the relationship between

energy efficiency and a preferred rate of ambulation?

The Center of Gravity (COG)

COG located at S1 - S2During preferred rate walking the

COG approximates a sinusoidal curve from the: Sagittal perspective - no greater than a

2” peak-to-valley excursion Frontal perspective - no greater than a

2” medial-to-lateral excursion

Path of the COG

Distortion of the Path of the COGA distorted path of the COG will

require mechanical and motor control compensations that will: Disrupt normal timing of events Over-ride normal gait control

Change from ‘automatic’ to ‘manua’l control strategies

Lead to over-correction of gait mechanics

The Result

Increased energy expenditure

A Simple ExampleWalking with a stiff-knee (“stiff-knee

gait”) with a cylinder castDuring stance the HAT will vault over

the fixed foot (especially during mid-stance)

COG will be deflected higher than the usual 2” upward vertical displacement with increased energy cost

Who Walks with a Stiff Knee?Transient knee injury patient (e.g.,

surgical repair of a ligamentHemiplegic with loss of knee controlThe AK amputee with a locked-knee

prosthesisThe BK amputee with poor knee control

Should we consider each case the SAME?

The Control of GaitMotor control options:

‘Manual’ control theory - thinking about having to take a step each time you want to advance the foot forward

‘Automatic control theory - an automatic control system that accounts for gait mechanics without having to think about foot placement and other metrical details

Which one is it?

Think about this...

An Everyday OccurrenceYou’re walking along 23rd Street,

heading west toward your bus stopYou’re thinking about what was

discussed in Kinesiology class todayYou’re also thinking that there is a

lot a traffic and it’s going to take you forever to get home tonight...

QuestionsAre you thinking about foot placement?Are you thinking about how long each

step should be?Are you thinking about trunk and pelvic

rotation in the transverse plane and maintaining reciprocal arm-swing?

Are you thinking about...

AnswerProbably NOT!

Why?Your gait control is on ‘automatic pilot’

When do you have to think about gait control?

When there’s a perturbation

Central Pattern Generator (CPG)CPG - a group of synaptic connections

probably at the spinal cord level which are triggered by an event or condition

When a threshold is met via a triggering mechanism the CPG appears to be activated and takes over automatic control of gait metrics - i.e., you don’t have to think about it

EvidenceSpinalized (cord transected) cats

suspended over a treadmill will walk with an alternating, striding quadripedal gait

Human quadriplegics have also “walked” this way

CPG and Supraspinal InfluenceGait perturbations

Example: Someone walks across your path from the side that you didn’t see

There’s a need to take immediate corrective action to avoid a collision

Supraspinal centers appear to over-ride the CPG and switch to a ‘manual control’ strategy

What Triggers a CPG?There seems to be a close relationship

between activating a CPG for gait control and preferred rate of ambulation

In other words, there is a rate-dependent relationship between normal gait mechanics and its control mechanism

So...

It appears we maintain the path of the COG within very tight limits and therefore expend the least amount of energy by assuming a preferred rate which in turn leads to an activation of a CPG

Think About This...

What’s one of the most common things heard during gait training in a PT clinic?

“Mr. Jones, while you’re walking, I want to go…”

“...very slow!”

What are some possible implications of this?Mr. Jones will be safe - probably won’t

fall and break his hip (good news).Mr. Jones won’t sue you (good news).The path of the COG may be distorted

(bad news).Energy cost may increase (bad news)

Suppose Mr. Jones has a cardiac condition?

What are some possible implications of this?Mr. Jones may never reach his pre-

injury/disease preferred rate of ambulation and therefore never trigger a CPG that automates gait (bad news).

Mr. Jones’ gait may never look ‘normal’ (bad news).

Is it possible that...

…going very slow might actually cause Mr. Jones to lose his balance and fall?

Why?

Factors That Lead to the Initiation of GaitAssume right LE will advance first:

Weight shift to left LE (unloads right hip)Left hip moves into (hyper-) extension and

precedes right hip flexionRight side of pelvis rotates medially

preceding right hip flexionCOG moves over right foot after it’s

advanced

Factors That Lead to the Initiation of GaitSuccessful completion of these

events probably leads to a triggering of a CPG as preferred rate is attained

Gait Training Scenario

Mrs. Flanagan is standing in the parallel bars with her physical therapist, Dudley Doright, getting ready to take a left step to start walking.

We hear the PT say, “Now, Mrs. Flanagan, I want you to put your left foot forward and take a step…”

What wrong with this picture?Where is the patient’s COG relative to

her base-of-support?What is probably the size of the left

step (step length) relative to the right?What impact will this likely have on her

forward velocity?What are the chances of attaining her

pre-injury/disease preferred rate?

Deficit-Oriented Gait AnalysisQuestions:Do diseases/injuries specifically

manifest as a stereotypical gait pattern?

orDoes the disease/injury lead to a

deterioration of control parameters which cause gait deficits?

ResponseIf you believe the latter…it shouldn’t

matter what the patient’s problem is

If you understand the consequence of the disease or injury (loss of motor control, weakness, damaged supportive structures, loss of a part of or an entire limb, etc.)...

…you should be able to anticipate or predict what impact a deficit has on gait irrespective of their state of injury or disease.

Hip Extensors - Stance

Analysis of Deficits Hip Extensors - StanceEarly stance (@

HS) Prevent hip flexion

(jack-knifing)Early stance (HS -

FF) Guide hip into

flexion eccentrically

Early stance (@ HS) weakness/absence Hip/trunk collapses

into flexionEarly stance (HS -

FF) Trunk falls forward

Hip Abductors - Stance

Hip AbductorsPrevent contra-lateral hip from dipping

greater than 5 - 80

Stance-side abductors active

Loss of abductors: Static analysis - + Trendelenburg sign Dynamic analysis - weakness o f abductors

manifests as ‘lurching gait’ (toward stance- side)

Analysis of Deficits Abductors - StanceEarly stance

COG shifts away from stance side LE

Increases moment arm of COG relative to stance side hip

Stance side abductors generate counter-rotational torque to prevent contra-lateral from dropping > 5-80

Early stance weakness/absence Contra-lateral hip

drops > 5-80 Compensation is to

lean (‘lurch’) over stance-side LE

Quadriceps - Stance

Analysis of Deficits Quadriceps - StanceEarly stance (HS -

FF) Guides knee into 200

of flexion eccentrically (controls unlocking of the knee)

Late stance (HR - TO) Controls for knee

flexion (~400 at TO)

Early stance weakness/absence Inability to absorb energy Buckling

Late stance weakness/absence Knee collapse into flexion

-premature flexion into early swing - ‘rubber knee’

Pre-Tibial Group - Stance

Analysis of Deficits Pre-tibial Group - StanceEarly stance (HS -

FF) Lowers forefoot to

floor eccentrically After forefoot

contacts floor- pull tibia forward over foot

Early stance weakness/absence Forefoot slaps to

the floor - ‘drop-foot’ gait

Loss of forward pull of tibia

Plantar Flexors - Stance

Analysis of Deficits Plantar Flexors - StanceLate mid-stance

Concentrically pulls tibia forward

Late stance (HR - TO) Provides propulsive

thrust during push off

Early stance weakness/absence Loss of forward pull

of tibia Loss of forward

thrust - poor transition to early swing

Ankle Stability - Late StanceAnkle less stable and subject to injury

(e.g., sprains) in plantar flexion vs.dorsiflexion Posterior trochlea in mortise Collateral ligaments swing out of collateral

position

Position of ankle during push-off (late stance) = plantar flexed

Analysis of Deficits Peroneals - StanceLate stance (HR -

TO) Dynamically

provide collateral stability to ankle when plantar flexed

Secondary plantar flexor for forward thrust

Late stance weakness/absence Ankle instability

causing medial-lateral movement

Potential for ankle injury - sprains

Poor transition from late stance to early swing

Analysis of Deficits Plantar Intrinsics - StanceLate stance (HR - TO)

Provide medial - lateral stability to MTP joints (especially nos. 1 & 2) - cancels second degree of freedom

Improves forward propulsion and transition to early swing

Late stance weakness/absence Excessive medial -

lateral ‘shimmy’ of hindfoot during HR

Inefficient forward thrust

Paraspinals -Stance

Analysis of Deficits Paraspinals - StanceEarly stance (HS -

FF) & late stance (HR - TO) Prevent forward

flexion of trunk acting on pelvis

Early & late stance weakness/absence Trunk falls forward Loss of head and

neck control

Analysis of Deficits Hip Flexors - SwingLate stance - early

swing (acceleration) Forward flexion of

femur working with plantar flexors to accelerate LE in early swing

Functionally shortens LE (with eccentric action of quadriceps and dorsiflexors) to prevent ‘toe-drag’

Late stance - early swing weakness/absence of forward acceleration after TO

Toe may not clear the floor during swing through Compensate with

circumduction at hip

Dorsiflexors - Swing

Analysis of Deficits Dorsiflexors - SwingMid-to-late swing

(deceleration) Affects ‘toe-up’

concentrically Functionally

shortens LE during swing through

Mid-to-late swing weakness/absence Loss of ‘toe-up’ Compensation

Increased hip flexion - ‘steppage gait’

Circumduction at hip

Hamstrings - Swing

Analysis of Deficits Hamstrings - SwingLate swing

(deceleration) Decelerates tibial

shank Provides for smooth

transition between late stance and early swing

Late swing weakness/absence ‘Impact on terminal

extension’ - knee slapped into extension or hyperextension

Gait in the Elderly Men - Murray, Kory & Clarkson

Gait did not appear vigorous or labored

Gait pattern did not resemble that of patients with CNS damage

Gait was guarded and restrained - attempt to maximal stability and security

Gait in the Elderly Men - Murray, Kory & Clarkson

Gait resembled someone walking on a slippery surface decreased step &

stride legnth wider dynamic BOS increased lateral

head movement decreased rotation

of pelvis

Gait in the Elderly Men - Murray, Kory & Clarkson

toe/floor clearance distance slightly decreased

lower stance-to-swing ratio

decreased reciprocal arm swing more from elbow than shoulder

Spasticity and its Impact on GaitSpasticity - resistance to passive stretch

Results from CNS (UMN) injury/disease Increased source of uncontrolled/poorly

controlled tension Probably due to loss of inhibiting action of

the CNS While tension production may be significant

the time-rate-of-tension development may be delayed

Spasticity & GaitSpastic response may be caused by:

Unexpected quick stretch of muscles Foot contact with floor Supraspinal overlay

Effects: Restrict joint excursion Delay transition from one gait phase to

the next

Spasticity & GaitDubo et al. showed that EMG activity

of spastic muscles increased during mid-stance i.e., there was a loss of phasic control of muscles

Spasticity & Gait ExamplesQuadcriceps

May prevent knee from unlocking during interim between HS and FFKnee maintained in extension leading to a

‘vaulting’ over stance limb or circumduction of hip

Disrupts (timing) transition to mid- and late stance

May prevent LE bending during swing phase

Spasticity & Gait ExamplesPlantar flexors

Increase in spastic tone may limit forward rotation of tibia between MS and POMay locate ground reaction force well behind

knee causing significant flexion moment during late MS and knee buckling tendency

Ankle may be locked up during PO decreasing propulsive thrust forward - inefficient transition from TO to early swing

Spasticity & Gait ExamplesHamstrings

May limit forward swing of LE - decreasing step length

May prevent knee from reaching a terminally extended position just prior to HS

Gait Training - QuestionsIf gait is controlled by a rate-

dependent chain of synaptic connections at the spinal cord level (i.e., a CPG), is it possible for a PT to effect (physiological) changes in the gait control system?

Gait Training - QuestionsIf gait is initiated (and sustained) as

described previously (e.g., unloading of hip, pelvis rotates medially, COG loads over stance foot, etc.), how do we train patients to start walking?

Gait Training - QuestionsWhat impact will ‘assistive devices’

have on gait performance? Parallel bars Walkers Bilateral & unilateral crutches and canes PTs using contact guarding from the

side or behind

Gait Training - QuestionsIf the rhythmic, symmetrical

alternating characteristics of gait are triggered when a patient assumes their preferred rate, will gait symmetry and a ‘normal’ appearing gait be possible if the patient walks substantially slower than her preferred rate?

Gait Training - QuestionsAre all patients’ objectives concerning

walking the same?Are your objectives for Ms. Walksalot, a

39 year old healthy female who broke her ankle two weeks ago in an intensive tennis match, the same as for Mr. Livesinathirdstorywalkup, a frail 87 year old male, with emphysema and a fractured, pinned hip?

Gait Training - QuestionsWhat’s the best thing a PT can say to

their patient while gait training?...

...Probably very little!