Gait Cycle Analysis

High Yield Overview

GAIT CYCLE ANALYSIS

The gait cycle is the repeating sequence of limb movements from initial contact

60%

—prevalence

—blue

Gait Phases

Stance (60%)

PatternContact -> Loading -> Mid -> Terminal

TreatmentWeight Acceptance

Swing (40%)

PatternPre -> Initial -> Mid -> Terminal

TreatmentLimb Advancement

Critical Must-Knows

Definition: The gait cycle is the repeating sequence of limb movements from initial contact of one foot to the next contact of the same foot, consisting of stance (60%) and swing (40%) phases
Mechanism: Coordinated neuromuscular control and biomechanical forces produce efficient bipedal locomotion through alternating periods of single and double limb support
Management: Understanding gait cycle phases enables diagnosis of pathological gait patterns, guides orthopaedic treatment planning, and informs rehabilitation protocols

Examiner's Pearls

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Exam point to remember
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Exam point to remember
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Exam point to remember

Clinical Imaging

Imaging Gallery

High Yield Exam Points

Stance vs Swing Ratio

Stance phase: 60% of gait cycle. Swing phase: 40%. Double support: 20% (10% at beginning and end of stance). Single support: 40%. These percentages are exam favorites.

Muscle Activation Sequence

Initial contact: ankle dorsiflexors eccentric. Loading response: quadriceps eccentric. Terminal stance: gastrocnemius-soleus plantarflexion. Pre-swing: hip flexors initiate swing. Know the timing.

Ground Reaction Forces

Vertical GRF shows double-hump pattern: first peak at loading response (110% body weight), second peak at terminal stance (120% body weight). Anterior-posterior force shows braking then propulsion.

Pathological Gait Patterns

Trendelenburg: weak hip abductors (gluteus medius). Antalgic: shortened stance on painful limb. Steppage: foot drop (weak dorsiflexors). Equinus: tight gastrocnemius. Know the underlying causes.

At a Glance

The gait cycle is the repeating sequence of limb movements from heel strike to next heel strike, divided into stance phase (60%) and swing phase (40%). Double support occurs for 20% of the cycle (10% at beginning and end of stance). Critical muscle activations include eccentric dorsiflexors at initial contact, eccentric quadriceps during loading, and gastrocnemius-soleus push-off at terminal stance. Recognise pathological patterns: Trendelenburg (weak hip abductors), antalgic (shortened stance on painful side), steppage (foot drop from weak dorsiflexors), and equinus (tight gastrocnemius).

Mnemonic

I Love My Two PillowsPhases of Stance Phase

I - Initial contact (heel strike)

L - Loading response (foot flat)

M - Midstance (single limb support)

T - Terminal stance (heel off)

P - Pre-swing (toe off)

Memory Hook:Think of resting on pillows through the stance phase from heel to toe

Mnemonic

I Must TryPhases of Swing Phase

I - Initial swing (acceleration)

M - Mid-swing (foot clearance)

T - Terminal swing (deceleration)

Memory Hook:Like swinging a baseball bat: accelerate, maintain arc, decelerate

Mnemonic

PELVIC KneeGait Determinants of Perry

P - Pelvic rotation (4 degrees forward on swing side)

E - Elevation of pelvis (pelvic tilt on swing side)

L - Lateral displacement of pelvis (4-5 cm side to side)

V - Vertical displacement of center of mass (5 cm rise and fall)

I - Initial contact knee flexion (15 degrees)

C - Controlled knee flexion during stance (reduces vertical displacement)

Knee - Knee and ankle interactions minimize energy expenditure

Memory Hook:Perry's PELVIC movements plus Knee mechanics reduce energy cost of walking

Overview

Definition

The gait cycle represents one complete sequence of walking from the initial ground contact of one foot to the subsequent ground contact of the same foot. [1] Normal human gait is characterized by alternating periods of single and double limb support, with each limb progressing through a repeating sequence of stance and swing phases that enable efficient forward progression while maintaining balance and minimizing energy expenditure. [2]

Temporal Parameters

Gait Cycle Division:

Stance Phase: 60% of the gait cycle (from initial contact to toe-off)
Swing Phase: 40% of the gait cycle (from toe-off to next initial contact)
Double Support: 20% of the cycle (10% at beginning and 10% at end of stance)
Single Support: 40% of the cycle (when contralateral limb is in swing)

The stance-to-swing ratio changes with walking speed, with faster speeds showing decreased stance time and increased swing time. [1,2]

Speed-Dependent Variables:

Cadence: 90-120 steps per minute (normal adult walking)
Stride length: 1.2-1.5 meters (distance between successive contacts of same foot)
Step length: 0.6-0.8 meters (distance between contacts of opposite feet)
Walking velocity: 1.2-1.4 meters per second (average adult)

These parameters vary with age, gender, height, and pathology. [3]

Epidemiology and Clinical Relevance

Gait analysis is fundamental to orthopaedic assessment:

Diagnosis: Identifies specific gait abnormalities indicating underlying pathology
Treatment planning: Guides surgical interventions (lengthening, osteotomy, fusion)
Outcome assessment: Objective measurement of intervention effectiveness
Rehabilitation: Informs physical therapy protocols and assistive device prescription

Three-dimensional gait analysis is the gold standard for quantifying gait deviations in cerebral palsy, neuromuscular disorders, and complex deformities. [4,5]

Gait Cycle Phases and Characteristics

Stance Phase (60% of Cycle)

Stance Phase Subdivisions

1. Initial Contact (0-2% of cycle)

Biomechanics:

First moment when foot touches ground (historically termed "heel strike")
Hip: 30 degrees flexion
Knee: Near full extension (0-5 degrees flexion)
Ankle: Neutral position (0 degrees)
Foot: Supinated position preparing for contact

Muscle Activity:

Tibialis anterior: Maximum activity (eccentric) to control plantarflexion
Quadriceps: Beginning activation to prepare for loading
Hamstrings: Active to decelerate forward swing of leg
Gluteus maximus: Active to control hip flexion

Ground Reaction Force:

Vertical force begins to rise from zero
Posterior force component (braking) begins
Center of pressure at heel contact point [1,6]

2. Loading Response (0-10% of cycle)

Biomechanics:

Period from initial contact to contralateral toe-off
Represents first period of double support
Hip: 30 degrees flexion maintained
Knee: Flexes to 15-20 degrees (shock absorption)
Ankle: Plantarflexes 10-15 degrees (controlled by dorsiflexors)
Foot: Progresses from supination to pronation

Muscle Activity:

Quadriceps: Eccentric contraction (critical for controlled knee flexion)
Tibialis anterior: Eccentric contraction (controls foot slap)
Hip abductors (gluteus medius/minimus): Activate to stabilize pelvis
Hip extensors: Continue activity from initial contact

Ground Reaction Force:

Vertical force rapidly increases to first peak (110% body weight)
Braking force reaches maximum
Lateral force shows small lateral component
This phase is critical for shock absorption and weight acceptance [1,6,7]

3. Midstance (10-30% of cycle)

Biomechanics:

Single limb support phase begins
Body weight passes over supporting foot
Hip: Extends from 30 to 0 degrees
Knee: Extends from 15-20 degrees to 5 degrees
Ankle: Dorsiflexes from 10 degrees plantarflexion to 5 degrees dorsiflexion
Foot: Pronated and flattened (shock absorption)

Muscle Activity:

Ankle plantarflexors (gastrocnemius-soleus): Begin activity to control tibial advancement
Hip abductors: Maximum activity (single limb support stability)
Quadriceps: Decreasing activity as knee extends
Intrinsic foot muscles: Active for arch support

Ground Reaction Force:

Vertical force decreases from first peak to valley (80-90% body weight)
Braking force transitions to propulsive force
Center of pressure moves anteriorly along foot [1,6,7]

4. Terminal Stance (30-50% of cycle)

Biomechanics:

From heel rise to contralateral initial contact
Hip: Continues extension to 10-20 degrees hyperextension
Knee: Remains near full extension (0-5 degrees flexion)
Ankle: Dorsiflexes to maximum (10 degrees) as tibia advances over foot
Foot: Heel rises, weight transfers to forefoot

Muscle Activity:

Gastrocnemius-soleus: Maximum activity (concentric plantarflexion for push-off)
Hip extensors: Continue activity
Intrinsic foot muscles: Maximum activity for rigid lever formation
Tibialis posterior: Active for supination and arch support

Ground Reaction Force:

Vertical force increases to second peak (120% body weight)
Propulsive force reaches maximum
Center of pressure at metatarsal heads
This phase generates forward propulsion [1,6,7]

5. Pre-swing (50-60% of cycle)

Biomechanics:

From contralateral initial contact to toe-off
Second period of double support
Hip: Neutral to slight flexion
Knee: Rapidly flexes to 40 degrees
Ankle: Plantarflexes to 20 degrees (passive)
Foot: Final push-off from hallux

Muscle Activity:

Hip flexors (iliopsoas, rectus femoris): Begin activation for swing initiation
Ankle dorsiflexors: Begin activation preparing for swing
Gastrocnemius-soleus: Decreasing activity
Adductor longus: Active for limb advancement

Ground Reaction Force:

Vertical force rapidly decreases to zero
Propulsive force decreases
Center of pressure at toe [1,6,7]

Swing Phase (40% of Cycle)

Swing Phase Subdivisions

6. Initial Swing (60-73% of cycle)

Biomechanics:

From toe-off to feet adjacent
Acceleration phase of swing
Hip: Rapidly flexes to 20 degrees
Knee: Flexes to maximum (60 degrees) for toe clearance
Ankle: Dorsiflexes from plantarflexion toward neutral
Foot: Clears ground by approximately 1 cm

Muscle Activity:

Hip flexors (iliopsoas): Concentric contraction for limb advancement
Tibialis anterior: Active to achieve foot clearance
Short head of biceps femoris: Assists hip flexion
Rectus femoris: Active for both hip flexion and knee extension initiation

Ground Reaction Force:

No ground contact (zero force on swinging limb)
Contralateral limb in single support [1,8]

7. Mid-swing (73-87% of cycle)

Biomechanics:

From feet adjacent to tibia vertical
Hip: Continues flexion to 30 degrees
Knee: Begins extension from 60 to 30 degrees (passive pendular motion)
Ankle: Achieves neutral position (0 degrees)
Foot: Maintains clearance

Muscle Activity:

Tibialis anterior: Maintains dorsiflexion for clearance
Hip flexors: Continue activity
Quadriceps: Begin activity to extend knee
Hamstrings: Begin activity to decelerate knee extension

Ground Reaction Force:

No ground contact
Minimum muscle activity during this phase (most efficient part of gait) [1,8]

8. Terminal Swing (87-100% of cycle)

Biomechanics:

From tibia vertical to next initial contact
Deceleration phase
Hip: Maintains 30 degrees flexion
Knee: Extends to near full extension (0-5 degrees flexion)
Ankle: Maintains neutral dorsiflexion
Foot: Prepares for initial contact

Muscle Activity:

Hamstrings: Maximum activity (eccentric) to decelerate knee extension
Tibialis anterior: Maintains ankle dorsiflexion
Quadriceps: Active to achieve full knee extension
Gluteus maximus: Begins activation for upcoming stance

Ground Reaction Force:

No ground contact until next initial contact [1,8]

Joint Kinematics and Range of Motion

Joint Motion During Gait

Hip Joint Motion

Sagittal Plane (Flexion-Extension):

Maximum flexion: 30 degrees (at initial contact and terminal swing)
Neutral: 0 degrees (at midstance)
Maximum extension: 10-20 degrees (at terminal stance)
Total range of motion: 40-50 degrees

Coronal Plane (Abduction-Adduction):

Small amplitude motion (5-7 degrees total)
Slight abduction during single limb support
Returns to neutral during double support

Transverse Plane (Internal-External Rotation):

Internal rotation during loading response (5 degrees)
External rotation during terminal stance (5 degrees)
Total rotation: approximately 10 degrees

The hip joint serves as the primary controller of limb advancement and body progression. [9]

Knee Joint Motion

Sagittal Plane (Flexion-Extension):

Initial contact: 0-5 degrees flexion
Loading response: 15-20 degrees flexion (shock absorption)
Midstance: 5 degrees flexion
Terminal stance: 0-5 degrees flexion
Pre-swing: 40 degrees flexion
Initial swing: Maximum flexion 60 degrees
Terminal swing: Returns to 0-5 degrees

Two Flexion Waves:

First wave: Loading response flexion (shock absorption)
Second wave: Swing phase flexion (toe clearance)

The knee demonstrates the largest range of motion of any lower extremity joint during gait (0-60 degrees). [9,10]

Ankle Joint Motion

Sagittal Plane (Dorsiflexion-Plantarflexion):

Initial contact: Neutral (0 degrees)
Loading response: 10-15 degrees plantarflexion (controlled)
Midstance to terminal stance: Progressive dorsiflexion to 10 degrees
Pre-swing: Rapid plantarflexion to 20 degrees
Swing phase: Return to neutral dorsiflexion

Critical Functions:

Controlled plantarflexion prevents foot slap
Dorsiflexion accommodates forward tibial progression
Plantarflexion generates propulsive power
Neutral position enables toe clearance [9,10]

Foot and Subtalar Motion

Pronation-Supination Sequence:

Initial contact: Supinated (rigid structure for heel contact)
Loading response to midstance: Pronation (shock absorption, adaptation)
Terminal stance: Resupination (rigid lever for push-off)

This pronation-supination cycle is essential for:

Shock absorption during loading
Adaptation to uneven terrain
Conversion to rigid lever for propulsion [11]

Muscle Activation Patterns

Neuromuscular Control

Ankle Dorsiflexors (Tibialis Anterior)

Activation Timing:

Terminal swing to initial contact: Concentrically activate to achieve neutral ankle position
Loading response: Eccentrically contract (maximum activity) to control plantarflexion and prevent foot slap
Swing phase: Active throughout to maintain toe clearance

Clinical Significance:

Weakness produces foot drop and steppage gait
Excessive activity seen in spastic gait patterns [6,12]

Ankle Plantarflexors (Gastrocnemius-Soleus)

Activation Timing:

Midstance to terminal stance: Progressive increase in activity
Terminal stance: Maximum concentric contraction for push-off (second rocker)
Pre-swing: Rapidly decreasing activity

Power Generation:

Gastrocnemius-soleus complex generates majority of propulsive power
Contributes to forward acceleration of center of mass
Critical for normal walking speed and efficiency [6,12]

Quadriceps Muscle Group

Activation Timing:

Terminal swing: Begins activation to extend knee
Initial contact to loading response: Maximum eccentric activity to control knee flexion (critical for shock absorption)
Midstance: Decreasing activity as knee extends

Clinical Significance:

Weakness produces instability during loading response
May cause knee hyperextension or flexed knee gait as compensation [12]

Hamstring Muscle Group

Activation Timing:

Terminal swing: Maximum eccentric activity to decelerate knee extension and control hip flexion
Initial contact: Continue activity for hip extension
Loading response to midstance: Decreasing activity

Dual Function:

Decelerate lower leg during terminal swing
Assist hip extension during early stance [12]

Hip Abductors (Gluteus Medius and Minimus)

Activation Timing:

Loading response through midstance: Maximum activity during single limb support
Terminal stance: Decreasing activity

Critical Function:

Stabilize pelvis in coronal plane during single limb support
Prevent contralateral pelvic drop (Trendelenburg sign)
Weakness produces characteristic Trendelenburg gait [12,13]

Hip Flexors (Iliopsoas)

Activation Timing:

Pre-swing: Begin activation to initiate swing
Initial swing to mid-swing: Continue activity for limb advancement
Terminal swing: Decreasing activity

Function:

Primary driver of swing phase initiation
Advance limb forward during swing [12]

Ground Reaction Forces

Kinetic Analysis

Vertical Ground Reaction Force

Characteristic Pattern:

Loading response: Rapid rise to first peak (110% body weight)
Midstance: Decrease to valley (80-90% body weight)
Terminal stance: Increase to second peak (120% body weight)
Pre-swing: Rapid decrease to zero

Double-Hump Pattern:

First peak: Weight acceptance and impact absorption
Valley: Single limb support with body passing over foot
Second peak: Push-off and propulsion
Shape varies with walking speed and pathology [7,14]

Anterior-Posterior Ground Reaction Force

Braking and Propulsion:

Loading response to midstance: Posterior (braking) force reaches maximum (15-20% body weight)
Midstance: Transition from braking to propulsion
Terminal stance: Anterior (propulsive) force reaches maximum (20-25% body weight)

Net Effect:

Braking force decelerates forward progression
Propulsive force accelerates body forward
Forces approximately equal in normal gait (net zero horizontal acceleration) [7,14]

Mediolateral Ground Reaction Force

Lateral Stability:

Small amplitude forces (5% body weight)
Medially directed during loading response
Laterally directed during terminal stance
Maintains mediolateral stability [7,14]

Center of Pressure Progression

Path During Stance:

Initial contact: Lateral heel
Loading response to midstance: Progresses along lateral border of foot
Terminal stance: Moves medially toward metatarsal heads
Pre-swing: Terminates at hallux

This progression reflects the foot's rocker mechanism and weight transfer pattern. [11,14]

Gait Determinants and Energy Conservation

Perry's Six Determinants of Gait

Saunders, Inman, and Eberhart described six major determinants that minimize energy expenditure during normal gait by reducing vertical and lateral displacement of the center of mass. [15]

1. Pelvic Rotation

Mechanism: Pelvis rotates approximately 4 degrees forward on the swing side
Effect: Effectively lengthens the limb during initial contact and terminal swing
Energy saving: Reduces amplitude of vertical displacement of center of mass

2. Pelvic Tilt

Mechanism: Pelvis drops approximately 5 degrees on the swing side (contralateral hip adduction)
Effect: Lowers the peak of vertical displacement during single limb support
Energy saving: Flattens the sinusoidal curve of center of mass trajectory

3. Knee Flexion During Stance

Mechanism: Knee flexes 15-20 degrees during loading response
Effect: Lowers the body during what would otherwise be highest point
Energy saving: Reduces vertical displacement amplitude

4. Foot and Ankle Motion

Mechanism: Foot serves as rocker in three phases (heel, ankle, forefoot)
Effect: Smooths the forward progression of center of mass
Energy saving: Prevents abrupt changes in velocity

5. Knee Mechanism

Mechanism: Coordinated knee flexion-extension pattern throughout stance
Effect: Works with ankle motion to smooth progression
Energy saving: Reduces energy required for limb advancement

6. Lateral Pelvic Displacement

Mechanism: Pelvis shifts laterally approximately 4-5 cm from side to side
Effect: Keeps center of mass closer to supporting limb
Energy saving: Reduces need for excessive hip abductor force

Clinical Application: Loss of any determinant (e.g., fused knee, ankle arthrodesis) increases energy cost of walking by requiring greater muscular effort and increased vertical displacement. [15,16]

Pathological Gait Patterns

Common Gait Abnormalities

Antalgic Gait

Characteristics:

Shortened stance phase on painful limb
Rapid transfer of weight to opposite limb
Decreased vertical ground reaction force on affected side
May show decreased hip and knee motion

Causes:

Arthritis (hip, knee, ankle)
Fracture or stress fracture
Muscle strain or tendinopathy
Any painful lower extremity condition [17]

Trendelenburg Gait

Characteristics:

Contralateral pelvic drop during stance on affected limb
Trunk lean toward affected side (compensated Trendelenburg)
Decreased stance time on affected side

Causes:

Gluteus medius weakness or paralysis
Hip joint pathology (arthritis, developmental dysplasia)
L5 radiculopathy (superior gluteal nerve)
Post-hip surgery (nerve injury) [13,17]

Steppage Gait (Foot Drop)

Characteristics:

Exaggerated hip and knee flexion during swing phase
Foot slap at initial contact
Dragging toe if compensation inadequate

Causes:

Common peroneal nerve palsy
L5 radiculopathy
Anterior compartment syndrome
Peripheral neuropathy
Sciatic nerve injury [17]

Equinus Gait (Toe Walking)

Characteristics:

Initial contact with forefoot instead of heel
Excessive plantarflexion throughout stance
Shortened stride length
May show knee hyperextension (compensation)

Causes:

Gastrocnemius-soleus contracture
Achilles tendon shortening
Cerebral palsy (spastic)
Clubfoot (residual or recurrent)
Idiopathic toe walking (children) [17]

Vaulting Gait

Characteristics:

Excessive plantarflexion on stance limb
Rising up on toes to clear opposite limb
Seen during swing phase of affected limb

Causes:

Functional leg length discrepancy
Inability to flex knee or dorsiflex ankle on swing side
Compensation for inadequate limb clearance [17]

Circumduction Gait

Characteristics:

Swing limb traces semicircular path
Hip abduction and external rotation during swing
Increased energy expenditure

Causes:

Limb length discrepancy
Knee or ankle fusion/stiffness
Hip flexor weakness
Spasticity (stroke, cerebral palsy) [17]

Spastic Gait (Hemiplegic)

Characteristics:

Affected limb held in extension
Circumduction during swing phase
Equinovarus foot position
Decreased knee flexion during swing

Causes:

Stroke (cerebrovascular accident)
Traumatic brain injury
Cerebral palsy (hemiplegic type) [17]

Parkinsonian Gait

Characteristics:

Shuffling steps with reduced stride length
Decreased arm swing
Flexed posture (trunk, hips, knees)
Festinating gait (rapid small steps)
Difficulty initiating movement

Causes:

Parkinson disease
Parkinsonism (drug-induced, vascular) [17]

Clinical Gait Assessment

Observational Gait Analysis

Systematic Visual Assessment

Lateral View:

Initial contact: Heel strike, knee extended, ankle neutral
Loading response: Knee flexion, controlled plantarflexion
Midstance: Tibia advances over foot, knee extends
Terminal stance: Heel rise, ankle dorsiflexion
Pre-swing: Toe-off, rapid knee flexion
Swing phase: Knee flexion peak, ankle dorsiflexion

Anterior/Posterior View:

Pelvic stability during single limb support
Hip abduction-adduction
Knee varus-valgus alignment
Foot progression angle (internal/external rotation)
Base width (normal: 5-10 cm)

Common Deviations to Identify:

Decreased stance time (antalgic)
Excessive pelvic drop (Trendelenburg)
Knee hyperextension (quadriceps weakness, knee instability)
Foot slap (dorsiflexor weakness)
Toe walking (equinus contracture) [17,18]

Instrumented Gait Analysis

Three-Dimensional Motion Analysis:

Gold standard for quantifying gait deviations
Uses multiple cameras and reflective markers
Measures joint angles in three planes
Calculates joint moments and powers
Essential for complex deformity assessment (cerebral palsy) [4,5]

Force Plate Analysis:

Measures ground reaction forces in three directions
Calculates center of pressure trajectory
Determines temporal parameters
Assesses asymmetry between limbs [14]

Electromyography (EMG):

Records muscle activation timing and amplitude
Identifies abnormal muscle firing patterns
Guides treatment (e.g., selective dorsal rhizotomy, botulinum toxin) [12]

Evidence Base and Key Studies

Temporal and Spatial Gait Parameters

Expert Consensus

Perry J, Burnfield JM • Gait Analysis: Normal and Pathological Function (2010)

Clinical Implication: This evidence guides current practice.

Ground Reaction Forces in Normal Gait

Biomechanical Analysis

Winter DA • Biomechanics and Motor Control of Human Movement (2009)

Clinical Implication: This evidence guides current practice.

Muscle Activation Patterns During Gait

Observational Study

Sutherland DH, et al. • Journal of Bone and Joint Surgery (1980)

Clinical Implication: This evidence guides current practice.

Energy Cost of Pathological Gait

Comparative Study

Waters RL, Mulroy S • Journal of Bone and Joint Surgery (1999)

Clinical Implication: This evidence guides current practice.

Gait Determinants Theory

Biomechanical Theory

Saunders JB, Inman VT, Eberhart HD • Journal of Bone and Joint Surgery (1953)

Clinical Implication: This evidence guides current practice.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Normal Gait Cycle Fundamentals

EXAMINER

"An examiner asks you to describe the phases of the gait cycle and their relative durations. They then ask about the muscle activity patterns during these phases."

EXCEPTIONAL ANSWER

The gait cycle is divided into stance phase, comprising 60% of the cycle, and swing phase, comprising 40%. Stance phase is further subdivided into five functional phases: initial contact, loading response at 0-10% where the first period of double support occurs, midstance from 10-30% representing single limb support, terminal stance from 30-50% ending at contralateral initial contact, and pre-swing from 50-60% which is the second period of double support. Swing phase has three subdivisions: initial swing, mid-swing, and terminal swing. During loading response, the quadriceps contract eccentrically to control knee flexion for shock absorption, while tibialis anterior controls foot plantarflexion eccentrically to prevent foot slap. During terminal stance, the gastrocnemius-soleus complex generates maximum concentric force for push-off and propulsion. The hip abductors, particularly gluteus medius, are maximally active during midstance to stabilize the pelvis during single limb support. Understanding these phases and muscle activation patterns is essential for identifying pathological gait and planning treatment interventions.

KEY POINTS TO SCORE

Stance 60%, swing 40%, double support 20% total

Five stance subdivisions, three swing subdivisions

Quadriceps eccentric in loading response (shock absorption)

Gastrocnemius-soleus concentric in terminal stance (propulsion)

Hip abductors active midstance (pelvic stability)

COMMON TRAPS

✗Confusing percentages of stance vs swing phases

✗Forgetting that double support occurs twice (10% at start and 10% at end of stance)

✗Not knowing muscle contraction types (eccentric vs concentric)

✗Missing the clinical relevance of each phase

LIKELY FOLLOW-UPS

"What happens to stance-swing ratio with increased walking speed?"

"Describe the ground reaction force pattern during stance phase"

"How would quadriceps weakness affect the gait cycle?"

VIVA SCENARIOStandard

Scenario 2: Pathological Gait Patterns

EXAMINER

"A 65-year-old patient presents with a noticeable limp. On observation, you note that the pelvis drops on the right side when standing on the left leg. The examiner asks you to explain this finding and its underlying causes."

EXCEPTIONAL ANSWER

This patient is demonstrating a Trendelenburg gait pattern. The Trendelenburg sign occurs when the pelvis drops toward the unsupported side during single limb stance, indicating weakness or dysfunction of the hip abductor muscles, primarily gluteus medius and minimus, on the stance limb. Normally, these muscles contract forcefully during the single limb support phase of stance to stabilize the pelvis and prevent contralateral drop. When the patient stands on the affected left leg, the weakened left hip abductors cannot adequately stabilize the pelvis, resulting in the right-sided pelvic drop. Possible causes include hip abductor muscle weakness from superior gluteal nerve injury, L5 radiculopathy, direct muscle injury, or hip joint pathology such as osteoarthritis or developmental dysplasia that mechanically disadvantages the abductors. Some patients compensate by leaning their trunk toward the affected side during stance, which is termed a compensated Trendelenburg gait, as this shifts the center of mass closer to the hip joint and reduces the abductor moment arm requirement. Treatment depends on the underlying cause and may include physical therapy for strengthening, gait aids to reduce abductor demand, or surgical intervention for structural hip problems. This gait pattern significantly increases energy expenditure and can lead to secondary problems including low back pain and contralateral hip overload.

KEY POINTS TO SCORE

Trendelenburg sign: pelvic drop on unsupported side during stance

Caused by hip abductor weakness (gluteus medius/minimus)

Common causes: nerve injury, radiculopathy, hip joint pathology

Compensated form: trunk lean toward affected side

Increases energy expenditure significantly

COMMON TRAPS

✗Confusing which side is weak (stance side, not dropped side)

✗Forgetting to mention superior gluteal nerve

✗Not discussing compensatory mechanisms

✗Missing the functional impact on energy expenditure

LIKELY FOLLOW-UPS

"How would you test for hip abductor weakness on examination?"

"What is the difference between compensated and uncompensated Trendelenburg?"

"Describe the biomechanics of why the abductors are so important"

VIVA SCENARIOStandard

Scenario 3: Energy Conservation Mechanisms

EXAMINER

"The examiner presents a patient with bilateral ankle arthrodesis who complains of fatigue with walking. They ask you to explain why ankle fusion increases the energy cost of gait."

EXCEPTIONAL ANSWER

Ankle arthrodesis eliminates the normal ankle joint motion that is critical for energy-efficient gait. Perry and colleagues described six gait determinants that minimize energy expenditure by reducing vertical and lateral displacement of the center of mass. The ankle contributes to several of these determinants. First, the normal ankle functions as three rockers during stance: the heel rocker at initial contact, the ankle rocker during midstance as the tibia advances over the fixed foot, and the forefoot rocker during terminal stance push-off. These rockers smooth the forward progression of the center of mass and prevent abrupt velocity changes. With ankle fusion, the patient loses the ankle rocker function, forcing compensation through increased hip and knee motion, which requires greater muscular effort. Second, normal ankle plantarflexion-dorsiflexion motion works in coordination with knee flexion during stance to minimize vertical displacement of the center of mass. Loss of this coordination increases the amplitude of vertical rise and fall, increasing potential and kinetic energy requirements. Third, the ankle's contribution to push-off power is lost or reduced, requiring compensation from the hip flexors and contralateral limb for forward propulsion. Studies have shown that bilateral ankle arthrodesis can increase the metabolic cost of walking by 20-30% compared to normal gait. Additionally, the loss of normal foot and ankle motion eliminates the shock absorption function during loading response, transmitting greater forces to proximal joints. To minimize fatigue, patients may benefit from rocker-bottom shoes to partially restore the rocker mechanism, physical therapy to optimize compensatory strategies, and energy conservation techniques.

KEY POINTS TO SCORE

Ankle provides three rockers: heel, ankle, forefoot

Rockers smooth center of mass progression and reduce velocity changes

Ankle-knee coordination minimizes vertical displacement

Loss of push-off power requires compensation

Bilateral fusion increases metabolic cost 20-30%

COMMON TRAPS

✗Not knowing Perry's six gait determinants

✗Failing to explain the rocker mechanism specifically

✗Missing the quantitative increase in energy cost

✗Not offering practical solutions (rocker shoes)

LIKELY FOLLOW-UPS

"List all six of Perry's gait determinants"

"How does knee fusion differ from ankle fusion in terms of energy cost?"

"What is the role of the gastrocnemius-soleus in power generation?"

MCQ Practice Points

High-Yield MCQ Topics

Temporal Parameters

Stance phase = 60% of gait cycle
Swing phase = 40% of gait cycle
Double support = 20% total (10% at beginning and end of stance)
Single support = 40% of cycle
As walking speed increases, stance time decreases and swing time increases

Ground Reaction Forces

First peak: 110% body weight (loading response)
Valley: 80-90% body weight (midstance)
Second peak: 120% body weight (terminal stance)
Braking force maximum: 15-20% body weight
Propulsive force maximum: 20-25% body weight

Joint Range of Motion

Hip: 30 degrees flexion to 20 degrees extension (total 50 degrees)
Knee: 0-60 degrees flexion (maximum at initial swing)
Ankle: 10 degrees dorsiflexion to 20 degrees plantarflexion (total 30 degrees)

Muscle Activation

Loading response: quadriceps eccentric (shock absorption)
Terminal stance: gastrocnemius-soleus concentric (propulsion)
Midstance: hip abductors maximum (pelvic stability)
Terminal swing: hamstrings eccentric (knee deceleration)

Pathological Gait Recognition

Trendelenburg = hip abductor weakness (gluteus medius)
Steppage = foot drop (tibialis anterior weakness)
Antalgic = shortened stance on painful side
Equinus = toe walking (gastrocnemius contracture)

Australian Context

Australian Clinical Practice

Gait Analysis Services

Major Gait Laboratories in Australia:

Royal Children's Hospital Melbourne: Paediatric gait laboratory
Children's Hospital at Westmead, Sydney: Three-dimensional gait analysis
Queensland Paediatric Rehabilitation Service: Comprehensive motion analysis
Victorian Paediatric Rehabilitation Service: Cerebral palsy gait assessment

Clinical Practice Guidelines

Australian Cerebral Palsy Guidelines (2020):

Recommend three-dimensional gait analysis before multilevel surgery
Guide selection of appropriate interventions based on gait deviations
Inform timing of surgical interventions

NHMRC Guidelines:

Support evidence-based gait analysis for complex neuromuscular conditions
Recommend instrumented analysis when clinical observation insufficient

Research and Education

Australian Gait Research Centers:

University of Melbourne: Biomechanics and gait research
University of Queensland: Motion analysis and rehabilitation
La Trobe University: Musculoskeletal biomechanics

These institutions contribute to international gait analysis literature and train clinicians in advanced gait assessment techniques.

MCQ Practice Points

Exam Pearl

Q: What are the phases of the gait cycle and their relative durations?

A: Stance phase: 60% of cycle (heel strike to toe-off). Swing phase: 40% of cycle (toe-off to heel strike). Stance subdivided: initial contact (0-2%), loading response (2-12%), mid-stance (12-31%), terminal stance (31-50%), pre-swing (50-60%). Double limb support occurs at 0-12% and 50-60%.

Exam Pearl

Q: What are the six determinants of gait described by Saunders?

A: 1) Pelvic rotation (4° each direction), 2) Pelvic tilt (5° drop on swing side), 3) Knee flexion in stance (15-20°), 4) Foot mechanisms (ankle plantarflexion/dorsiflexion), 5) Knee mechanisms, 6) Lateral displacement of pelvis. These minimize vertical and lateral center of mass displacement, reducing energy expenditure.

Exam Pearl

Q: What muscle activity occurs during loading response phase of gait?

A: Tibialis anterior: Eccentric contraction controlling plantarflexion (foot slap prevention). Quadriceps: Eccentric contraction controlling knee flexion. Gluteus maximus/medius: Hip stabilization. This phase absorbs impact forces as body weight transfers onto the limb. Peak ground reaction force occurs here.

Exam Pearl

Q: What causes Trendelenburg gait?

A: Weakness of hip abductors (gluteus medius/minimus) on stance side causes contralateral pelvis to drop during single-limb support. Patient compensates with trunk lean toward affected side (compensated Trendelenburg). Causes: L5 radiculopathy, superior gluteal nerve injury, hip pathology, abductor mechanism failure post-THA.

Exam Pearl

Q: What is the center of mass displacement during normal gait?

A: Normal gait has approximately 5cm vertical displacement (sinusoidal pattern, lowest at double support, highest at mid-stance) and 4cm lateral displacement (side to side with each step). The determinants of gait minimize these excursions. Greater displacement = increased energy expenditure.

Management Algorithm