Introduction to gait analysis

Foot Clearance

• Occurs during the Initial Swing Phase of Gait
• Time period: 60-73% of gait cycle
• Purpose: To lift the foot off the ground to avoid dragging
• Swing Phase: The portion of the gait cycle where the foot is not in contact with the ground
• Initial Swing Phase: The first portion of swing phase

Terminal Swing

• Time period: 87-100% of gait cycle
• Begins with the tibia in a vertical position
• Ends with Initial Contact (IC)
• Limb advancement is complete
• Shin/shank moves forward (anteriorly) of the thigh

Displacement of Center of Mass (CoM)

• Normal values:
  • Vertical: 5 cm
  • Medial-Lateral: 4 cm
• Peaks in CoM displacement occur at:
  • 30% of gait cycle
  • 80% of gait cycle
• These peaks happen during mid-stance for the left and right legs respectively
• The Center of Mass is the balance point of an object

Joint Kinematics: Gait Analysis

• Gait analysis uses a 3-dimensional approach:
  • Sagittal Plane
  • Frontal Plane
  • Horizontal Plane
• It considers the movement of all joints:
  • Head
  • Arm
  • Trunk
  • Pelvis
  • Hip
  • Knee
  • Foot
• It looks at the movement from two perspectives:
  • Bottom-Up
  • Top-Down

Sagittal Plane Kinematics

• Sagittal plane: divides the body into left and right halves

• Segment	Motion	Total Arc of Motion
  Pelvis	Anterior and posterior tilt	2-4 degrees
  Hip	Flexion and extension	~40 degrees
  Knee	Flexion and extension	~60 degrees
  Ankle	Dorsiflexion and plantarflexion	~30 degrees

Frontal Plane Kinematics

• Frontal plane: Divides the body into anterior and posterior halves

• Segment	Motion	Total Arc of Motion
  Pelvis	Up and down obliquity (abduction/adduction)	6-8 degrees
  Hip	Abduction and adduction	~10 degrees
  Knee	Abduction (valgus) and adduction (varus)	~5 degrees
  Ankle	Inversion and eversion	~8 degrees

Horizontal Plane Kinematics

• Horizontal plane: Divides the body into top and bottom halves

• Segment	Motion	Total Arc of Motion
  Pelvis	Anterior/Posterior rotation (forward/backward)	~6-8 degrees
  Hip	Internal and external rotation	~15 degrees
  Knee	Internal and external rotation	~10 degrees
  Ankle	Negligible	n/a

Summary of Horizontal Plane Kinematics

• Focuses on the direction of motion, not absolute joint position
• During the First Half of Stance:
  • Pelvis, femur, and tibia rotate internally (IR)
  • Subtalar joint everts
  • Mid-tarsal joint increases pliability
• During the Second Half of Stance:
  • Pelvis, femur, and tibia rotates externally (ER)
  • Subtalar joint inverts
  • Mid-tarsal joint increases stability
• During Swing:
  • Pelvis, femur, and tibia rotate internally (IR)
  • Subtalar joint everts
  • Mid-tarsal joint increases pliability

Muscle Activity During Walking

• Most muscles contract in short bursts:
  • Duration: 100-400 ms
  • Percentage of gait cycle: 10-40%
• Understanding muscle function is important for:
  • Understanding gait deviations
  • Treatment planning

Types of Quantitative Gait Analysis

• Quantitative gait analysis focuses on measuring different factors during gait
• Types of quantitative analysis:
  • Gait Rite System
  • Plantar Pressure
  • 3D Coordinate System
  • Marker Placement
  • Electromyography

Gait Rite System

• A 14-foot long assessment mat with over 16,000 sensors
• Measures forces and pressures applied to the mat during walking

Plantar Pressure

• Uses Tekscan or Novel Pedar Systems
• Measures pressure distribution across the plantar surface of the foot
• Helps assess foot biomechanics during walking

3D Coordinate System

• Uses optical-based systems with markers placed on limbs and joints
• Multiple force plates are utilized
• Captures 3-dimensional movement data
• Helps analyze joint angles and movements

Pediatric Gait Analysis

• Specialized gait analysis for children, including:
  • Children's Hospital Zurich, Switzerland
  • Royal Children's Hospital, Melbourne, Australia
  • Children's Memorial Hospital, Chicago, IL
• Adjusts techniques and equipment to meet the specific needs of children

Electromyography

• Examines muscle activity
• Uses surface electrodes or fine-wire electrodes
  • Surface electrodes: Placed on the skin
  • Fine-wire electrodes: Inserted into the muscle with a small gauge needle
• Detects electrical activity in the muscles
• Provides information on muscle activation patterns during gait

Gait Assessment

• Range from simple observations to complex lab settings
• Qualitative or quantitative depending on equipment availability
• Goal is to identify:
  • Effectiveness and efficiency of walking
  • Potential impairments impacting ambulation
  • Safety and balance of the individual
  • Information for guiding interventions
• Understanding normal gait characteristics helps identify typical gait dysfunctions

Postural Assessment

• A static postural assessment is often the first step of a gait assessment
• It focuses on the position of the body while standing
• Provides insight into alignment, muscle imbalances, and potential gait deviations

Gait Cycle/Stride: Spatial Descriptors

• Step: Heel strike of one foot to heel strike of the other foot
• Stride: From heel strike of one foot to heel strike of the same foot (synonymous with gait cycle)
• Stride length: Distance from heel to same heel
• Step length: Distance from one heel strike to the opposite foot
• Step width: Distance between heels

Gait Cycle: Temporal Descriptors

• Cadence: Number of steps per minute:
  • Typical walking: 110-120 steps/min
  • Running: 170-180 steps/min
• Step time: Time taken for one right or left step
• Stride time: Time taken for one complete gait cycle/stride

Spatial-Temporal Descriptor

• Walking speed: Distance over time (m/s or mph)
  • Average walking speed: 1.37 m/sec (3 mph)
• Various measurement approaches can be used for assessing speed:
  • 10m walk test
  • 6-minute walk test
  • Self-selected pace
  • Fast pace
  • Predetermined pace

Normal Value Considerations

• Gait parameters vary based on age
• With increasing age, gait speed decreases, but cadence increases
• This age-related change can lead to intervention considerations for maintaining mobility and safety
• The specific age where these changes become relevant varies based on individual factors

Stance and Swing in Walking

• Each gait cycle consists of:
  • Stance phase: ~60% of the cycle
  • Swing phase: ~40% of the cycle

Rancho Los Amigos Terminology (Periods of Gait Cycle)

• Stance Phase:
  • Initial Contact (IC)
  • Loading Response (LR)
  • Midstance
  • Terminal Stance
  • Preswing
• Swing Phase:
  • Initial Swing
  • Midswing
  • Terminal Swing

Initial Contact (IC)

• Time period: 0% gait cycle
• Instant the foot makes contact with the ground
• An immediate reaction to body weight transfer occurs
• Marks the beginning of the stance phase
• Leads to impact deceleration

Loading Response (LR)

• Time period: 0-10% gait cycle
• The initial double limb stance period
• Continues from IC until the contralateral foot lifts for swing, creating double limb support
• Functions include:
  • Shock absorption
  • Weight bearing stability
  • Preservation of forward progression

Midstance

• Time period: 10-30% of the gait cycle
• First half of single limb support (SLS)
• Begins when the contralateral limb leaves the ground
• Ends when body weight is over the forefoot
• Main functions include:
  • Progression over the stationary foot
  • Limb and trunk stability to maintain balance

Terminal Stance

• Time period: 30-50% of the gait cycle
• Completes SLS
• Begins with heel rise
• Ends when the contralateral limb has IC
• Body weight shifts forward beyond the forefoot
• Functions include:
  • Progression of the body past the supporting foot
  • Limb and trunk stability for efficient walking

Preswing

• Time period: 50-60% of the gait cycle
• The final phase of stance, representing the second double limb stance period
• Begins with IC of the contralateral limb
• Ends with ipsilateral toe off
• Known as "weight release" or "weight transfer" as body weight is shifted to the other leg
• Muscle activation prepares the limb for the swing phase
• Functions include:
  • Positioning the limb for swing
  • Accelerating forward motion
  • Generating momentum for the swing phase

Initial Swing

• Time period: 60-73% of the gait cycle, approximately one-third of the swing period
• Begins when the foot is lifted off the ground
• Ends when the swing foot is opposite the stance foot
• Functions include:
  • Foot clearance to prevent dragging
  • Advancing the limb from a trailing position to a forward position

### Midswing

• Time period: 73-87% of the gait cycle, representing the middle one-third of swing
• Begins when the swing foot is opposite the contralateral (opposite) foot
• Ends when the swing limb is forward, and the tibia is in a vertical position
• Functions:
  • Limb advancement