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Quick Usage Guide for Your MUHS Exam

• Calcium in adolescence: 1300 mg/day
• Iron for adolescent girls: 26-28 mg/day (ICMR) / 15 mg (WHO)
• Protein for athletes: 1.2-2.2 g/kg/day
• Caloric deficit for weight loss: 500-750 kcal/day
• Creatine dose: 3-5 g/day
• Caffeine for performance: 3-6 mg/kg
• Female Athlete Triad / RED-S: low energy + menstrual dysfunction + low bone density
• WIFS program: 60 mg Fe + 500 mcg FA weekly for adolescent girls
• Weight loss rate: 0.5-0.75 kg/week (safe) - 1 kg fat = 7700 kcal

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MUHS MPT - Kinesiology of Gait: Topper-Level Answers

• Inman VT, Ralston HJ, Todd F - Human Walking, Williams & Wilkins, 1981
• Perry J, Burnfield JM - Gait Analysis: Normal and Pathological Function, 2nd Ed, SLACK Inc., 2010
• Neumann DA - Kinesiology of the Musculoskeletal System, 3rd Ed, Elsevier, 2016
• Norkin CC, Levangie PK - Joint Structure and Function, 5th Ed, FA Davis, 2011
• Rose J, Gamble JG - Human Walking, 3rd Ed, Lippincott Williams & Wilkins, 2006
• Miller's Review of Orthopaedics, 9th Ed, Elsevier, 2024
• Gage JR - The Treatment of Gait Problems in Cerebral Palsy, Mac Keith Press, 2004
• Sutherland DH - Gait Disorders in Childhood and Adolescence, Williams & Wilkins

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Q1. Components of Normal Gait (10 M) - Summer 2023

Introduction

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1. Gait Cycle (GC) - The Fundamental Unit

• Duration: ~1 second at comfortable walking speed
• Distance (stride length): ~1.5 m in adults
• Step length: ~0.75 m (right to left heel contact)
• Cadence: 100-120 steps/minute in adults
• Walking velocity: ~1.3-1.5 m/s

1. Stance Phase - 60% of GC
2. Swing Phase - 40% of GC

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2. Stance Phase (60% of Gait Cycle)

a. Initial Contact (IC) / Heel Strike (0% GC)

• Instant the reference foot contacts the ground
• Joint positions: Hip 25-30° flexion, Knee near full extension (0-5°), Ankle at neutral (0°) or slight plantarflexion
• Muscle activity:
  • Tibialis anterior (TA): eccentric contraction - controls foot slap, lowers forefoot gently
  • Quadriceps: eccentric contraction - prepares to accept body weight
  • Hamstrings: eccentric contraction - decelerating forward swinging limb
  • Gluteus maximus: concentric - stabilizes hip

b. Loading Response (LR) (0-12% GC) / Foot Flat

• Starts with IC and ends when contralateral foot leaves the ground
• Shock absorption, weight acceptance, and forward propulsion initiation
• Joint positions: Hip moves toward extension, Knee flexes 15-20° (shock absorber), Ankle plantarflexes 5-8° (controlled)
• Muscle activity:
  • Quadriceps: critical eccentric contraction - resists knee flexion (shock absorber)
  • Tibialis anterior: eccentric - controls foot flat
  • Gluteus medius: eccentric - controls pelvic drop on contralateral side
  • Iliopsoas: beginning elongation

c. Midstance (MSt) (12-31% GC)

• Single-limb support; body advances over the planted foot
• Begins when contralateral foot lifts off, ends when body's CoG passes directly over forefoot
• Joint positions: Hip extends from 25° flexion to neutral (0°), Knee extends back toward full extension (5°), Ankle dorsiflexes from 5° PF to 5° DF
• Muscle activity:
  • Gluteus medius: eccentric - controls Trendelenburg (prevents pelvic drop)
  • Quadriceps: minimal activity (passive knee extension by ground reaction force moving anterior to knee axis)
  • Soleus: eccentric - controls forward tibial progression over the fixed foot
  • Gluteus maximus: concentric - hip extension

d. Terminal Stance (TSt) (31-50% GC) / Heel Rise

• Begins with heel rise, ends when contralateral foot makes initial contact
• Joint positions: Hip extends to -10° (hyperextension), Knee slight flexion (5°), Ankle dorsiflexes to 10° DF (maximum DF)
• Muscle activity:
  • Gastrocnemius-Soleus: eccentric then concentric - controls ankle DF, then powers push-off
  • Hip flexors (iliopsoas): begin eccentric lengthening in preparation for swing

e. Pre-Swing (PSw) (50-62% GC) / Push-Off / Toe-Off

• Begins with IC of contralateral limb; ends with toe-off of reference foot
• Joint positions: Hip at 0° (neutral), Knee rapidly flexes to 35-40°, Ankle plantarflexes to 20°
• Muscle activity:
  • Gastrocnemius-Soleus: peak concentric activity - generates propulsive push-off force
  • Rectus femoris: eccentric - controls rapid knee flexion
  • Iliopsoas: concentric - initiates hip flexion for swing

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3. Swing Phase (40% of Gait Cycle)

a. Initial Swing (ISw) (62-75% GC)

• Begins when foot leaves ground (toe-off), ends when swinging foot is opposite the stance foot
• Joint positions: Hip flexes from 0° to 15°, Knee flexes to 60° (maximum), Ankle moves from 20° PF toward neutral
• Muscle activity:
  • Iliopsoas: concentric - hip flexion (primary swing initiator)
  • Hamstrings: eccentric - control hip flexion velocity
  • Tibialis anterior: concentric - dorsiflexes ankle for foot clearance

b. Midswing (MSw) (75-87% GC)

• Ends when swinging limb is forward with tibia vertical (perpendicular) to ground
• Joint positions: Hip 25° flexion, Knee extends from 60° to 25-30°, Ankle at neutral (0°)
• Muscle activity:
  • Tibialis anterior: concentric - maintains dorsiflexion for foot clearance
  • Quadriceps: minimal (passive knee extension by gravity and momentum)

c. Terminal Swing (TSw) (87-100% GC)

• Ends when foot makes Initial Contact with ground
• Joint positions: Hip 25-30° flexion, Knee full extension (0-5°), Ankle 0° (neutral-slight DF)
• Muscle activity:
  • Hamstrings: eccentric - decelerates the rapidly extending knee; most important activity here
  • Tibialis anterior: maintains dorsiflexion
  • Gluteus maximus: concentric - prepares for weight acceptance

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4. Temporal-Spatial Parameters of Normal Gait

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5. Double-Limb Support Periods

• Occur twice per gait cycle (at IC+LR and again at PSw)
• Each period ~10-13% of GC
• Together: ~20-26% of GC
• With increased speed: double-support decreases and eventually disappears (running = float phase)
• With decreased speed or fear of falling: double-support increases

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6. Center of Mass (CoM) Displacement

• Vertical displacement: ~5 cm total (rises at midstance, drops at double support)
• Lateral displacement: ~5 cm total (shifts over weight-bearing limb)
• Minimizing CoM displacement = minimizing energy expenditure (Saunders' 6 determinants)

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7. Muscle Action Summary Table

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Recent Advances

• 3D Motion Capture Systems (Vicon, Qualisys): provide precise kinematic and kinetic data for all 3 planes, replacing observational gait analysis in research
• Instrumented insoles and wearable sensors (IMUs - Inertial Measurement Units): allow real-time gait monitoring outside the lab; validated for clinical use (Tao et al, Sensors 2012)
• Functional Electrical Stimulation (FES) restores normal gait pattern in drop foot and hemiplegic patients by triggering tibialis anterior during swing
• AI-driven gait analysis: machine learning algorithms detect gait deviations from smartphone camera video with 85-95% accuracy (recent validation studies 2022-24)

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Q2. Kinesiological Impact of Knee Pain on Gait (10 M) - Summer 2022

Introduction

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1. Role of the Knee in Normal Gait (Baseline)

1. Shock absorption at IC/LR: 15-20° of flexion, powered by eccentric quadriceps
2. Foot clearance in swing: 60° of flexion powered by hamstrings and hip flexors

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2. Primary Kinesiological Changes in Knee Pain Gait

A. Antalgic Gait Pattern

• Shortened stance phase on the affected limb (body shifts weight rapidly off the painful knee)
• The contralateral swing phase is correspondingly shortened (faster step)
• Reduced walking velocity and cadence
• Reduced stride length
• Increased double-limb support time to minimize single-limb loading
• Increased step width for additional stability

• Miller's Review of Orthopaedics, 9th Ed, p. 867

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3. Phase-by-Phase Analysis of Kinesiological Changes

A. Initial Contact (IC)

B. Loading Response (LR)

• Normal: 15-20° knee flexion (eccentric quadriceps - shock absorption)
• With knee pain: Knee flexion is minimized or abolished
  • Patients "stiffened" the knee during LR to avoid the painful arc of motion
  • Quadriceps eccentric activity is reduced (fear of pain / pain inhibition)
  • Consequence: loss of shock absorption → increased impact forces transmitted to hip and lumbar spine
  • Compensatory trunk forward lean over the stance limb (reduces knee extension moment, reducing quadriceps demand)

C. Midstance (MSt)

• Normal: smooth tibia progression over foot with soleus eccentric control
• With knee pain:
  • Reduced knee ROM throughout stance
  • Stiff-knee gait during mid-stance
  • Gluteus medius may show altered timing and reduced amplitude → potential Trendelenburg sign
  • Hip abductor-adductor moment altered: patients laterally lean trunk over affected limb (reduces knee adduction moment - KAM)

D. Terminal Stance (TSt)

• Normal: heel rise with gastroc-soleus push-off; knee moves from 5° to 0°
• With knee pain:
  • Reduced or absent heel rise
  • Shortened push-off
  • Reduced propulsive force and reduced forward momentum
  • Patients avoid hyperextension moment at the knee during late stance

E. Pre-Swing (PSw) / Swing Phase

• Normal: knee flexes rapidly to 60°
• With knee pain (especially in anterior knee pain / patellar involvement):
  • Reduced knee flexion during swing (stiff-knee gait)
  • Compensatory hip hiking (quadratus lumborum) or circumduction to clear the foot
  • Reduced swing phase velocity

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4. Muscle Activation Changes

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5. Kinematic Changes Summary

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6. Kinetic Changes

• Reduced vertical ground reaction force (vGRF) peak on affected side
• Reduced push-off impulse (smaller second peak of vGRF curve - the "propulsive peak")
• Altered CoP (center of pressure) trajectory through the foot
• Reduced external knee flexion moment at IC (stiff-knee strategy)
• Increased knee adduction moment in medial compartment OA

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7. Long-Term Compensatory Changes (Pathological Sequelae)

1. Hip abductor weakness due to disuse and altered gait pattern
2. Contralateral limb overloading → contralateral knee/hip pain
3. Lumbar spine overload due to loss of knee shock absorption
4. Quadriceps atrophy from AMI and disuse → worsening instability (vicious cycle)
5. Ankle plantarflexor weakness from reduced push-off
6. Cartilage degradation worsening from altered load distribution

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Recent Advances

• Knee adduction moment (KAM) biofeedback training: real-time KAM feedback during gait retraining (medial OA) reduces KAM by 20-40%, decreases pain (Cheung et al, Gait & Posture 2018)
• Lateral wedge insoles: reduce KAM in medial compartment OA - simple, effective (AAOS clinical guideline)
• Treadmill gait retraining with trunk lean modification: evidence-based gait modification for patellofemoral and medial OA
• fMRI studies: show cortical reorganization of motor representation of quadriceps in chronic knee pain patients

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Q3. Patho-Kinesiological Changes in a Patient with Hand-to-Knee Gait for 19 Years (10 M) - Summer 2022

Introduction

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Background: Mechanism of Hand-to-Knee Gait

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Patho-Kinesiological Changes After 19 Years

A. Changes at the Knee Joint

1. Genu Recurvatum (Knee Hyperextension)
   • Over years, the patient learns to passively "lock" the knee in hyperextension rather than using the hand
   • The posterior knee capsule and ligaments become chronically overstretched
   • Ground reaction force falls anterior to the knee axis → passive extension maintained
   • Structural consequence: posterior capsule laxity, posterior horn meniscal stress, PCL elongation
   • Joint incongruence: abnormal tibiofemoral contact patterns → accelerated articular cartilage wear (particularly posterior tibial plateau)
2. Quadriceps Contracture/Atrophy
   • Chronic non-use → severe type II fiber atrophy
   • Residual quadriceps (if partial paralysis) show adaptive shortening in chronic flexion posture or lengthening in hyperextension posture
3. Hamstring Adaptive Changes
   • In hyperextension gait: hamstrings are chronically on stretch and develop adaptive lengthening
   • May develop hamstring tendinopathy at proximal attachment (ischial tuberosity)
4. Patellofemoral Joint Changes
   • Quadriceps atrophy → patellar tracking abnormalities
   • Lateral patellar tilt and subluxation due to iliotibial band tightness
   • Chondromalacia patella from abnormal patellar mechanics

B. Changes at the Hip Joint

1. Hip Flexor Tightness (Thomas Test positive)
   • Patient leans forward at the trunk during the stance phase
   • Chronic forward lean → adaptive shortening of iliopsoas
   • Hip flexion contracture (fixed at 10-20°) develops over years
2. Gluteus Maximus Weakness/Atrophy
   • If the original pathology involves gluteus maximus (L5/S1 nerve root, myopathy):
   • Chronic disuse → type II fiber atrophy
   • The patient demonstrates compensatory trunk extensor hyperactivity (backward lean of trunk at IC to move CoM behind the hip axis, eliminating need for active hip extension)
3. Gluteus Medius Changes
   • Altered pelvic kinematics from compensatory trunk lean
   • Trendelenburg gait may coexist if gluteus medius is also involved
   • Adductor tightness on the unaffected side
4. Hip Joint: Chronic altered loading → acetabular cartilage wear, potential osteophyte formation, reduced ROM

C. Changes at the Ankle and Foot

1. Plantarflexion Contracture (Equinus)
   • To compensate for the inability to flex the knee in swing, the ankle is kept in plantarflexion
   • Chronic plantarflexion during rest and ambulation → Achilles tendon contracture
   • Gastrocnemius-soleus adaptive shortening
   • Loss of dorsiflexion ROM (normally 10-15° during midstance)
2. Altered Push-Off
   • Reduced or absent propulsive plantarflexion at push-off (either from fatigue, contracture, or neurological involvement)
   • Compensatory hip hiking and trunk lateral lean to advance the limb
3. Foot Deformities
   • Claw toes: long toe flexors substitute for intrinsic weakness and proprioceptive loss
   • Pes cavus (high-arched foot) may develop in neurological conditions (post-polio, CMT disease)
   • Metatarsal stress fractures from chronic altered foot loading pattern

D. Changes at the Lumbar Spine

1. Lumbar Hyperlordosis
   • Compensates for hip flexion contracture - spine hyperextends to keep the CoM over the base of support
   • Facet joint overloading → degenerative facet OA
   • Disc compression - increased posterior disc pressure
2. Scoliosis
   • Chronic limb length discrepancy (functional - from altered gait mechanics) → compensatory lumbar scoliosis
   • Convexity typically toward the affected side
3. Paraspinal Muscle Changes
   • Ipsilateral quadratus lumborum overactive (compensatory hip hike)
   • Paraspinal hypertrophy on ipsilateral side with atrophy on contralateral side

E. Contralateral Limb Changes

1. Overloading: The unaffected limb carries a disproportionate load over 19 years
2. Knee and hip OA: 3-4x higher risk on the contralateral side (Shakoor N et al, Arthritis & Rheumatism 2002)
3. Faster cartilage degeneration from cumulative overloading
4. Fatigue fractures (calcaneus, metatarsals) from chronic overuse

F. Upper Extremity and Trunk

1. Upper limb overuse: 19 years of pressing the hand on the knee → lateral epicondylitis, wrist extension strain, shoulder fatigue
2. Trunk lateral flexor hypertrophy (ipsilateral QL) from chronic compensatory lean
3. Pectoralis minor tightness from forward head posture

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Summary Table: 19-Year Structural Adaptations

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Physiotherapy Implications

• Assessment priorities: Manual muscle testing of quadriceps and gluteus maximus, ROM at all joints, functional gait analysis, Berg Balance Scale
• Treatment: Progressive quadriceps strengthening (NMES, graded resistance), stretching hip flexors and Achilles, orthoses (KAFO for quad paralysis), gait retraining, core stabilization
• Orthotic management: Knee-ankle-foot orthosis (KAFO) with posterior knee stop prevents recurvatum while allowing ambulation without hand support

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Q4. Gait Deviations - Enumeration + Kinesiology of High Steppage Gait (10 M) - Winter 2022

Part A: Enumeration of Gait Deviations

I. Stance Phase Deviations

II. Swing Phase Deviations

III. Whole-Cycle Deviations

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Part B: Kinesiology of High Steppage Gait

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Cause of Foot Drop (Tibialis Anterior Weakness/Paralysis)

1. Eccentric contraction at IC - controls plantar flexion rate (prevents foot slap)
2. Concentric contraction during swing - dorsiflexes ankle for foot clearance

• Common peroneal nerve palsy (fibular head compression/trauma)
• L4, L5 nerve root lesion (disc prolapse, spinal stenosis)
• Peripheral neuropathy (DM, Guillain-Barré)
• Stroke/hemiplegia (UMN lesion with spastic plantarflexors)
• Anterior compartment syndrome
• ALS, Charcot-Marie-Tooth disease

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Kinesiological Analysis of Steppage Gait Phase by Phase

• IC: Instead of heel strike, the foot contacts the ground with the entire plantar surface (foot flat) or even toe-first
• Foot slap: If only partial weakness, the foot slaps the ground uncontrolled (no eccentric TA braking)
• LR/MSt: Largely normal if plantarflexors and proximal muscles are intact
• TSt/PSw: If only TA is affected, the push-off through gastrocsoleus may be preserved

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Kinesiological Reasoning for Exaggerated Hip and Knee Flexion

Additional length = foot length × sin(20°) ≈ 25 cm × 0.34 ≈ 8.5 cm

1. Increase hip flexion (by 20-25° extra) - the steppage strategy
2. Hike the hip (quadratus lumborum - lateral elevation of hemipelvis)
3. Circumduct the leg (swing the leg outward in an arc)

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Compensatory Strategies Used in Steppage Gait

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Energy Cost

• Larger excursion of hip and knee joints
• Increased muscle work to generate exaggerated flexion moments
• Disrupted momentum transfer
• Oxygen cost may be 20-40% higher than normal walking velocity

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Observation Points in Clinical Gait Analysis

• Foot slap at IC (absent in pure paralysis; present in partial weakness)
• Toe drag in swing if compensation is incomplete
• Characteristic "steppage" appearance: leg raised high with hip/knee flexion
• Absent heel strike → flat-foot initial contact
• Trendelenburg or hip hike may coexist

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Q5. Kinesiology of Six Determinants of Gait + Patho-Kinesiology of Deviations (10 M) - Winter 2022

Introduction

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DETERMINANT 1: Pelvic Rotation

• During each step, the pelvis rotates 4° internally and 4° externally (total 8°) in the horizontal/transverse plane
• During right IC: right pelvis rotates forward (internally) relative to the left
• This effectively lengthens the functional limb at the extremes of the step (IC and preswing)
• Prevents excessive drop of the CoM during double-limb support
• Net effect: flattens the peak of the CoM arc and reduces the vertical rise

• Reduced pelvic rotation → shorter step length, reduced forward momentum
• Seen in: Parkinson's disease (rigidity), lumbar spinal fusion, spinal cord injury
• CoM shows exaggerated vertical displacement → increased energy cost
• Excessive pelvic rotation (>8°): seen in hip abductor weakness to maintain step width

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DETERMINANT 2: Pelvic List (Lateral Tilt)

• The non-weight-bearing (swing) side pelvis drops 5° below the weight-bearing side
• This is a controlled drop by the eccentric contraction of the gluteus medius on the weight-bearing side
• Effect: the swinging limb's CoM drops at midstance, reducing the vertical rise of the CoM trajectory
• Net effect: reduces the peak of the CoM arc (flattens the sinusoidal path)

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DETERMINANT 3: Stance-Phase Knee Flexion (Early Knee Flexion)

• At IC, the knee is nearly fully extended; during LR, the knee flexes to 15-20°
• This lowers the CoM at IC, reducing the upward rise of CoM that would otherwise occur as the limb accepts weight
• The eccentric quadriceps contraction simultaneously absorbs the loading impact (shock absorption)
• Net effect: Reduces upward displacement of CoM at IC; reduces impact loading

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DETERMINANT 4: Ankle-Foot Mechanism

• Heel contacts ground; foot plantarflexes (controlled by eccentric TA)
• Creates a forward rotation of the body over the heel pivot point
• Lowers CoM smoothly

• Tibia advances forward over the fixed foot; ankle dorsiflexes (soleus eccentric)
• CoM smoothly advances forward (maintains forward momentum)

• Heel rises; body advances over the metatarsal heads
• Gastrocsoleus concentric push-off elevates CoM for next step

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DETERMINANT 5: Knee Motion (Interaction with Ankle-Foot)

• Works in concert with ankle-foot mechanism
• Knee flexes at IC (15-20°) → flattens the descent of CoM at weight acceptance
• Knee extends at midstance → elevates CoM for forward progression
• Knee flexes at pre-swing (35-40°) → reduces CoM rise as body vaults over forefoot
• The "knee flexion-extension-flexion" pattern in stance creates a smooth, low-amplitude CoM path

• Stiff-knee gait (reduced knee ROM in swing) increases CoM excursion in swing and increases energy cost by forcing circumduction or hip hiking

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DETERMINANT 6: Lateral Displacement of the Pelvis (Coronal CoM Control)

• During weight transfer to the stance limb, the pelvis shifts 5 cm laterally over the supporting limb
• This is controlled by:
  • Hip abductors (gluteus medius, minimus) preventing excessive lateral sway
  • Physiologic valgus angle of the femur (allows feet to be close together - narrow base of support)
  • Tibio-femoral valgus (coxa valgus + knee valgus = narrow base of support with medially angled femur)
• Narrow base of support (5-10 cm) = minimal lateral CoM shift = less energy expenditure

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Summary Table: Six Determinants

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Q6. Gait Analysis in Physiotherapy (30 M) - Summer 2023

Introduction

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I. HISTORICAL BACKGROUND

• Aristotle (350 BC): first scientific analysis of animal locomotion
• Borelli (1680): applied mechanics to human movement ("De Motu Animalium")
• Weber Brothers (1836): described step length, cadence, and walking velocity
• Eadweard Muybridge (1872-1887): first photographic analysis of locomotion (horse and human)
• Braune & Fischer (1895): first quantitative gait analysis using photography + markers
• Saunders, Inman & Eberhart (1953): described 6 determinants of gait
• Verne Inman (1966-1981): established University of California Berkeley Biomechanics Laboratory - foundation of modern clinical gait analysis
• Jacquelin Perry (1992): published Gait Analysis - the definitive clinical reference
• Gage JR (1991): introduced clinical gait analysis in cerebral palsy - revolutionized surgical planning

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II. PURPOSES OF GAIT ANALYSIS IN PHYSIOTHERAPY

1. Diagnosis and understanding of movement pathology
2. Outcome measurement before and after intervention (surgery, orthotics, physiotherapy)
3. Surgical planning (particularly in CP, stroke, neuromuscular disease)
4. Orthotic prescription and evaluation
5. Research into normal and pathological gait
6. Rehabilitation monitoring (objective measurement of progress)
7. Prevention of falls and gait-related injuries
8. Sports performance optimization

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III. TYPES OF GAIT ANALYSIS

A. OBSERVATIONAL GAIT ANALYSIS (OGA)

• Naked eye observation
• Video recording (sagittal and coronal planes; 2D)
• Structured observation checklists

1. Rancho Los Amigos (RLA) Observational Gait Analysis - the gold standard structured protocol
   • Observes 6 joints (trunk, hip, knee, ankle, subtalar, toes)
   • Across 8 phases of the gait cycle
   • Records deviations using a standardized form
2. Edinburgh Visual Gait Score (EVGS)
3. Gillette Gait Index

• Observe from anterior, posterior, lateral (bilateral) views
• Video the patient from all planes at minimum 30 fps
• Slow-motion playback for phase-by-phase analysis
• Standard assessment order: whole-body then joint-specific; proximal-to-distal

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B. KINEMATIC ANALYSIS

1. 3D Motion Capture (Gold Standard)

• Plug-in Gait (PiG): most widely used; 16-39 markers
• Helen Hayes Hospital marker set
• Oxford Foot Model (OFM): for detailed foot analysis

• Joint angles in 3 planes (sagittal, frontal, transverse)
• Joint angular velocities and accelerations
• Segment linear velocities

• Firestein & Kelley's Textbook of Rheumatology (Fig. 6.2)

2. 2D Video Analysis

• Camera in sagittal or coronal plane
• Manual or automatic digitization of markers
• Dartfish, Kinovea software for 2D angle analysis
• Less accurate than 3D but widely used clinically

3. Inertial Measurement Units (IMUs)

• Accelerometers + gyroscopes + magnetometers
• Worn on body segments (shank, thigh, pelvis, foot)
• Calculate joint angles via sensor fusion algorithms
• Systems: Xsens MVN, APDM Opal, Delsys
• Advantages: Portable; no lab required; real-time; low cost
• Validated for: stride length, cadence, sagittal plane kinematics
• Current evidence: IMUs show excellent agreement with 3D motion capture for sagittal plane variables (ICC 0.85-0.95) (Cloete T et al, Sensors 2021)

4. Footprint Analysis (Pedobarography / Footprint Method)

• Inkpad method: patient walks over inked paper; measures step and stride length, step width, foot angle
• Simple, low-cost spatiotemporal analysis
• GAITRite Electronic Walkway: pressure-sensitive mat; records step length, stride length, cadence, walking speed, double support time automatically
• Widely used in fall risk assessment (Elderly), Parkinson's, neurological rehab

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C. KINETIC ANALYSIS

1. Force Platforms (Force Plates)

• Fz (vertical): characteristic double-peak M-shaped curve (first peak ~1.2x BW at LR; valley at midstance; second peak ~1.1x BW at push-off)
• Fy (anterior-posterior): braking force at IC; propulsive force at push-off
• Fx (mediolateral): lateral sway forces

• Joint moments: internal moments (muscle forces) and external moments (GRF × moment arm)
• Joint power: moment × angular velocity (positive = energy generation; negative = energy absorption)
• Knee Adduction Moment (KAM): key metric for medial compartment OA loading
• Total support moment: sum of hip + knee + ankle extension moments (determines fall risk)

• Surgical planning in CP: identify primary vs. compensatory deviations
• Evaluating prosthetic gait
• Measuring treatment outcomes in OA, post-stroke rehabilitation
• Sports performance (vertical jump, sprinting mechanics)

2. Plantar Pressure Analysis (Pedobarography)

• Emed (Novel), Pedar, F-Scan
• Measures pressure distribution under the foot during stance
• Applications: diabetic foot ulcer prevention (identifies high-pressure areas); orthotic prescription; post-fracture rehabilitation; assessment of flatfoot/cavus foot

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D. ELECTROMYOGRAPHIC ANALYSIS (EMG)

• Surface EMG (sEMG): electrodes placed over muscle belly; non-invasive; records overall muscle activity
• Fine-wire/Intramuscular EMG: needle or fine-wire inserted into muscle; required for deep muscles (tibialis posterior, iliopsoas)

• Muscle onset and offset timing
• Amplitude (relative activity)
• Duration of activity
• Co-contraction indices

1. Diagnosing spastic muscles in UMN lesions: differentiating overactive vs. appropriately compensatory muscles
2. Pre-surgical planning in CP: dynamic polyelectromyography distinguishes true spasticity from compensatory activity
3. Biofeedback during gait retraining (EMG-triggered FES)
4. Sports performance: technique optimization

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E. ENERGY ANALYSIS

• Portable metabolic systems (Cosmed K4b², MOXY): measure VO2, VCO2, energy expenditure during gait
• Physiological Cost Index (PCI): Heart rate-based estimate of energy cost
  • PCI = (Walking HR - Resting HR) / Walking Speed
  • Normal: 0.2-0.4 beats/m
  • Higher values indicate less energy-efficient gait

• Evaluating gait efficiency after orthoses/prostheses
• Monitoring rehabilitation progress in neurological patients
• Comparing pathological vs. normal energy cost

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F. TEMPORAL-SPATIAL PARAMETERS

• Walking velocity: 1.2-1.5 m/s
• Cadence: 100-120 steps/min
• Stride length: 140-160 cm
• Step width: 5-10 cm

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IV. INTEGRATED (FULL-SERVICE) GAIT LABORATORY

1. 3D motion capture (kinematics)
2. Force platforms (kinetics)
3. EMG (muscle activity)
4. Video (qualitative)
5. Optional: metabolic cart, pedobarograph

• Joint angles (kinematics)
• Joint moments and powers (kinetics)
• Muscle timing (EMG)
• Energy expenditure (metabolic)

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V. CLINICAL APPLICATIONS IN PHYSIOTHERAPY

1. Cerebral Palsy

• Gold standard for surgical planning ("single-event multilevel surgery - SEMLS")
• Differentiates: true equinus vs. apparent equinus (hip flexion contracture)
• Gage's classification of CP gait patterns (Gage JR, 1991)
• Reduces "birthday surgeries" (annual surgery) by planning comprehensively

2. Stroke Rehabilitation

• Identifies compensatory vs. primary gait deviations
• Monitors progress of gait retraining (AFO prescription, FES, Lokomat treadmill)
• Hemiplegic gait features: equinovarus foot, stiff-knee swing, Trendelenburg, circumduction, shortened stance phase on affected side

3. Total Hip/Knee Arthroplasty

• Pre-operative gait analysis identifies compensatory strategies
• Post-operative gait analysis monitors restoration of normal kinematics and kinetics
• KAM measurement guides implant alignment planning (Andriacchi TP, CORR 2005)

4. Lumbar Spine

• Gait analysis identifies compensatory trunk and hip strategies for lumbar stenosis
• Post-surgical gait assessment (spinal fusion, disc replacement)

5. Pediatric Orthopaedics

• Growth plate monitoring in limb deformity
• Scoliosis and its gait consequences
• Developmental dysplasia of the hip (DDH)

6. Prosthetics and Orthotics

• Objective evaluation of prosthetic gait symmetry
• Orthotic prescription based on kinematic and kinetic deficits
• AFO design (floor-reaction, solid, hinged) based on stance/swing deficits

7. Parkinson's Disease

• Hypokinetic gait (reduced step length, cadence, arm swing, festination)
• Pre-post assessment of DBS (deep brain stimulation) effects
• Treadmill and cued-gait training efficacy

8. Fall Prevention in Elderly

• Gait variability (coefficient of variation of step time >3%) is the strongest predictor of falls (Hausdorff JM, Arch Intern Med 2001)
• Balance + gait training programs guided by analysis data

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VI. OUTCOME MEASURES USED WITH GAIT ANALYSIS

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VII. LIMITATIONS OF GAIT ANALYSIS

1. Laboratory environment does not replicate community walking conditions
2. Skin marker artifacts (soft tissue movement) introduce errors in kinematic data
3. Operator expertise: data interpretation requires specialized training
4. Cost and accessibility: full 3D gait labs cost INR 50 lakh-1 crore; limited to tertiary centers
5. Static vs. dynamic calibration issues
6. Variability: within-session and between-session variability must be accounted for
7. Cannot measure all parameters: muscle forces (internal), joint contact forces require modelling assumptions

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VIII. RECENT ADVANCES

1. Wearable IMU-based gait analysis (Xsens, APDM): fully portable gait assessment outside the lab; validated for community settings, home-based monitoring (Tao et al, Sensors 2012; Cloete T et al, 2021)
2. Markerless motion capture (OpenPose, MediaPipe, Azure Kinect): AI-based pose estimation from standard video cameras; eliminates need for reflective markers; accuracy approaching marker-based systems for sagittal kinematics (Colyer SL et al, Front Sports 2018)
3. Instrumented treadmills (Zebris, Bertec GRAIL): embedded force platforms + real-time visual feedback; enable gait retraining with perturbations and augmented feedback
4. Robot-assisted gait training (Lokomat, Ekso): exoskeletal devices provide body-weight supported treadmill training; gait analysis integrated into the device feedback loop
5. Digital gait analysis apps (Kinovea, PhysioTec, Sway): smartphone-based; democratize gait assessment for resource-limited settings
6. Musculoskeletal modeling (OpenSim, AnyBody): estimate muscle forces, joint contact forces, ligament loading from motion capture + force plate data - not directly measurable
7. Real-time biofeedback: EMG biofeedback, KAM biofeedback, and augmented feedback during gait training significantly improve outcomes (Shull PB et al, JNER 2013)
8. Artificial Intelligence in gait analysis: CNN and LSTM neural networks classify gait patterns (normal vs. pathological) from IMU data with >90% accuracy (Taborri J et al, Sensors 2020)

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Conclusion

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Q7. Analysis of Stance Phase of Gait Cycle + Hand-to-Knee Gait (20 M) - Summer 2020

Part A: Stance Phase Analysis

Joint-Specific Stance Phase Analysis

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Part B: Hand-to-Knee Gait

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Kinesiological Analysis

• At IC: knee immediately begins to buckle into flexion (collapses)
• The body's center of mass passes POSTERIOR to the knee axis
• No eccentric force to resist flexion moment

• A manual anterior force on the distal thigh or knee cap
• Creates a posterior-directed knee extension moment via the hip extensor chain
• This force + trunk forward lean (shifting CoM anterior to hip) keeps the knee extended
• Effectively replaces the absent quadriceps moment

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Phases of Gait in Hand-to-Knee Pattern

• IC: Patient leans trunk FORWARD over the affected limb + applies hand to knee
  • Forward trunk lean shifts CoM anterior to hip axis → passive hip extension moment keeps hip extended without gluteus maximus
  • Hand at knee provides the knee extension moment
• LR-MSt: Hand remains at knee throughout loading response
  • Patient may simultaneously use trunk extension (paraspinal muscles) to augment knee stability
• Late stance (TSt/PSw): Hand releases; patient weight shifts to contralateral limb

• Normal or near-normal if plantarflexors and hip flexors are intact
• May show compensatory hip hitching if hip flexors are also weak

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Associated Gait Deviations

1. Trunk forward lean at IC (to move CoM anterior to knee)
2. Reduced walking speed and cadence
3. Shortened stance phase on the affected side
4. Increased stance time on the unaffected side
5. Possible Trendelenburg if gluteus medius is also involved
6. Compensatory genu recurvatum (patient eventually learns to hyperextend the knee passively without the hand)
7. Reduced arm swing on the affected side (arm is used for knee support)

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Differential Diagnosis of Similar Patterns

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Physiotherapy Assessment

• Manual Muscle Testing: Quadriceps (L3, L4)
• Femoral nerve conduction and EMG
• Functional tests: Single-leg squat, step-up test
• Gait lab analysis: Kinetic data shows absent knee flexion moment at LR; kinematic data shows reduced stance-phase knee flexion

Physiotherapy Management

1. Quadriceps strengthening: progressive resistance training (PRE), NMES/EMS
2. Aquatic therapy: reduced gravity allows eccentric training without buckling risk
3. Orthotic support: Swedish knee cage, KAFO (knee-ankle-foot orthosis with posterior stop)
4. Gait retraining: progress from double-limb to single-limb weight-bearing
5. Proprioceptive training: balance exercises on unstable surfaces

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Q8. Role of Gait Analysis in Physiotherapy Diagnosis (10 M) - Summer 2019

Introduction

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1. Gait Analysis as a Diagnostic Tool

• Quadriceps grade 4/5 on MMT may be sufficient for normal gait, but kinetic analysis may reveal abnormal knee flexion moment
• A muscle that tests normal statically may be overactive or mistimed in dynamic function (common in spastic CP)
• Crouch vs. equinus: clinically similar appearance, but gait analysis reveals opposite kinematic findings

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2. Diagnosing Specific Conditions via Gait Analysis

A. Neurological Conditions

• Observational findings: equinovarus foot, stiff-knee swing, circumduction, Trendelenburg
• Kinematic findings: reduced ankle dorsiflexion, reduced knee flexion in swing, excessive hip circumduction
• Kinetic findings: reduced push-off power, increased KAM on affected side
• EMG: premature or prolonged activity of tibialis posterior and plantarflexors (spasticity); reduced tibialis anterior activity
• Diagnosis confirmed: True spasticity (velocity-dependent EMG increase) vs. fixed contracture (no velocity-dependent change)

• Reduced stride length (festinating gait)
• Increased double-support time
• Reduced arm swing
• Shuffling, flat-foot gait (absent heel strike)
• GAITRite or IMU-based analysis provides objective baseline for medication/DBS effects

• Gage's gait patterns: Pure equinus, Jump gait, Crouch gait, Apparent equinus, True equinus
• 3D gait analysis distinguishes these patterns and guides surgical decisions (SEMLS)
• Diagnostic question answered: Is the equinus due to spastic gastrocnemius, spastic tibialis posterior, bony deformity, or hip flexion contracture creating "apparent" equinus?

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B. Orthopaedic Conditions

• Diagnostic gait findings: reduced walking velocity, antalgic gait, reduced knee ROM in stance, elevated KAM (medial compartment loading), reduced push-off power
• KAM > 3% BW*m identifies patients at high risk of medial compartment progression (Miyazaki T et al, JBJS 2002)
• Guides: orthotic prescription (lateral wedge insole), surgical planning (HTO vs. TKA)

• Trendelenburg gait (abductor weakness from pain inhibition or true weakness)
• Reduced hip extension in stance (flexion contracture)
• Kinetics: altered hip moment; reduced abductor moment

• Quadriceps avoidance gait: reduced external knee flexion moment at LR (avoiding quad-loading which stresses the ACL-deficient knee)
• Identified only by kinetic analysis (not visible on observation)

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C. Post-Surgical Rehabilitation

• Pre-op gait identifies compensatory strategies
• Post-op serial gait analysis monitors: restoration of knee ROM, reduction of antalgic pattern, normalization of KAM
• Studies show 60-80% of TKA patients still have measurable gait deviations at 1 year (Andriacchi TP, CORR 2005)

• Monitors resolution of Trendelenburg pattern
• Measures symmetry of step length and walking velocity

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3. Distinguishing Primary from Compensatory Deviations

• Observed: Excessive knee flexion throughout stance (crouch)
• Primary cause options: a) Hamstring spasticity (prevents knee extension) b) Hip flexion contracture (pulling pelvis forward) c) Overlengthened gastrocnemius from previous surgery (excessive ankle DF = "calcaneus crouch")
• EMG identifies if hamstrings are truly spastic or compensating for weak quads
• Kinematics identifies if excessive knee flexion is isolated or coupled with hip flexion
• Without gait analysis: surgeon may lengthen hamstrings when the real problem is over-lengthened gastroc → making the patient worse (iatrogenic crouch)

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4. Documentation and Outcome Measurement

• Baseline gait analysis documents pre-treatment status
• Follow-up analysis measures treatment efficacy objectively
• Particularly important for: post-surgical follow-up, clinical trial research, medicolegal documentation

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5. Integration with Clinical Assessment

• Clinical history (onset, duration, previous treatments)
• Physical examination (ROM, strength, tone, reflexes)
• Imaging (X-ray, MRI)
• Neurological assessment

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Recent Advances in Diagnostic Gait Analysis

• Machine learning gait pattern recognition: Algorithms classify neurological gait disorders (Parkinson's, MS, ALS) with >90% accuracy from IMU data (Taborri et al, Sensors 2020)
• Gait analysis in fall prediction: Stride time variability (>3% CV) and dual-task gait cost are the strongest predictors of future falls in elderly (Hausdorff JM, Age & Ageing 2001)
• Remote gait monitoring: Wearable IMUs enable gait monitoring in the home environment; flagging gait deterioration before clinical presentation

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Q9. Methods of Kinematic Investigation of Gait (10 M) - Summer 2020

Introduction

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Classification of Kinematic Methods

1. Optical / Video-Based Methods
2. Inertial / Sensor-Based Methods
3. Electromagnetic Methods
4. Electrogoniometry
5. Footprint and Spatiotemporal Methods
6. Markerless / Computer Vision Methods (recent)

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1. Three-Dimensional Motion Capture (3D Optical)

• Cameras: 6-12 infrared cameras positioned around the walkway/lab
• Markers: 15-50 spherical retroreflective markers (diameter 9-25mm)
• Marker sets: Plug-in Gait (PiG), Helen Hayes, Cleveland Clinic, Oxford Foot Model
• Sampling rate: 100-200 Hz (captures fast movements)
• Volume: walkway of ~8-10m length

• Anterior/Posterior Superior Iliac Spines (ASIS, PSIS)
• Lateral thigh (thigh wand)
• Lateral femoral condyle
• Lateral/medial malleolus
• Calcaneus, 2nd metatarsal head

1. Raw marker coordinates → filtered (Butterworth low-pass filter, cutoff 6-10 Hz)
2. Segment coordinate systems computed from marker clusters
3. Joint angles calculated as relative orientation of adjacent segments (Euler angles)
4. Cadence, stride length, walking velocity calculated from temporal-spatial events

• Hip, knee, ankle joint angles in all 3 planes across the gait cycle
• Pelvic kinematics (tilt, obliquity, rotation)
• Trunk kinematics
• Segment velocities and accelerations

• Skin marker artifact: soft tissue movement introduces error (particularly at proximal thigh, pelvis)
• Requires reflective markers (time-consuming application)
• Lab-only (not community/outdoor use)
• Cost: INR 50 lakh+
• Technical expertise required

• Firestein & Kelley's Textbook of Rheumatology (p. 127)

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2. Two-Dimensional (2D) Video Analysis

• Digital video camera (min. 60 fps; high-speed 120-240 fps for detailed analysis)
• Calibration frame or reference grid
• Software: Kinovea (free), Dartfish, SIMI, Vicon Nexus 2D

• Camera positioned in the plane of interest (sagittal for flexion-extension; frontal for adduction)
• Markers or anatomical landmarks tracked frame-by-frame
• Angles calculated between body segments

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3. Inertial Measurement Units (IMUs)

• Accelerometer: measures linear acceleration (3 axes)
• Gyroscope: measures angular velocity (3 axes)
• Magnetometer: measures orientation relative to earth's magnetic field (3 axes)

• Segment orientations
• Joint angles
• Stride length, cadence, walking velocity

• Xsens MVN Analyze: full-body 17-sensor suit; near-3D motion capture accuracy
• APDM Opal: validated for Parkinson's gait analysis
• Shimmer sensors: research-grade, open-platform
• RehaGait: clinical IMU system for gait analysis

• Portable: usable outside the lab (community, home, stairs, outdoor terrain)
• Low cost: INR 1-10 lakh vs. INR 50 lakh+ for full 3D lab
• Real-time feedback: can be used for biofeedback during gait training
• Long-duration monitoring: capture daily walking patterns
• No marker attachment to skin

• Magnetic interference (ferromagnetic environments cause magnetometer errors)
• Drift in gyroscope signals (cumulative error over time)
• Lower accuracy for transverse plane motion vs. sagittal
• Requires sensor-to-segment alignment calibration

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4. Electrogoniometry

• Uniaxial goniometer: single plane (sagittal knee/ankle)
• Biaxial goniometer: two planes
• Triaxial (Spatial Parameter): three planes (used in research)

• Low cost; portable; real-time analog output
• No camera system needed
• Long recording duration (entire walking trial)
• Good for repetitive motion monitoring

• Measures only the joint it is attached to
• Attachment to skin introduces movement artifact
• Correct alignment to joint axis is technically demanding
• Uncomfortable for extended wear; limits natural gait

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5. Electromagnetic Motion Tracking

• No line-of-sight requirement (unlike optical systems)
• Smaller sensors than marker clusters

• Metal interference: ferromagnetic objects in the environment distort the magnetic field significantly
• Limited volume of measurement (~2-3m from transmitter)
• Less accurate than optical 3D capture

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6. Footprint Analysis and Spatiotemporal Methods

A. Ink Pad / Paper Method (Simple)

• Patient walks over ink-covered plate → footprints on paper
• Measures: step length, stride length, step width, foot angle (Fick angle)
• Advantages: Free; simple; no equipment
• Disadvantages: Only spatiotemporal data; no joint kinematics

B. GAITRite Electronic Walkway

• Pressure-sensitive mat (5-6m long, 0.89m wide) embedded with sensors (16,128 pressure sensors)
• Captures footfall positions and timing as patient walks across
• Outputs: step length, stride length, cadence, velocity, single/double support %, step width, heel-to-heel base of support
• Validated against: 3D motion capture; ICC 0.95-0.99 for spatiotemporal parameters
• Clinical use: Fall risk assessment; Parkinson's monitoring; post-THA/TKA gait analysis; pediatric gait

C. Portable Instrumented Walkways and Treadmills

• Zebris treadmill: pressure measurement + kinematics integrated
• Bertec GRAIL: treadmill + force plates + virtual reality perturbation

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7. Markerless Motion Capture (Computer Vision / AI-Based)

• OpenPose (Carnegie Mellon): open-source; 2D/3D pose from RGB video
• MediaPipe (Google): real-time 3D pose estimation on smartphones
• Microsoft Azure Kinect: depth camera + RGB; markerless 3D skeleton
• Theia Markerless (commercial): lab-grade accuracy without markers

• No marker application (saves time; no artifacts)
• Uses standard cameras (low cost)
• Suitable for clinical settings without gait labs
• Can analyze unconstrained gait (community settings)

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Summary Comparison Table

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Recent Advances

• Smartphone gait analysis: Apps validated for spatiotemporal gait parameters; IMU built into modern smartphones (iOS, Android) measures cadence, step length, walking speed with reasonable accuracy (Pradeep Kumar D et al, Gait & Posture 2020)
• Continuous home-based gait monitoring: IMU patches (long-wear, waterproof) capture 1000s of steps/day; identify gait deterioration before clinical presentation in Parkinson's and MS
• 4D scanning: Simultaneous 3D geometry + temporal sequence from multiple depth cameras (e.g., 4D Views); eliminates soft-tissue artifact by modeling entire body surface
• Inertial + EMG fusion: Combining IMU kinematics with EMG provides both movement and muscle data outside the lab - the future of portable gait analysis

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Quick Examination Reference: Key Numbers and Facts for Viva