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Gait Analysis - Detailed Orthopaedic Review

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1. Definitions and Terminology

• Step: Distance between successive initial contact (IC) by the two lower limbs (one foot to the opposite foot)
• Stride: Distance between successive IC by the same lower limb (= two steps; one complete gait cycle)
• Cadence: Number of steps per unit of time (steps/min)
• Velocity: Ratio of distance to time (cadence x step length)
• Walking is defined by always having at least one foot in contact with the ground, plus a period of double-limb support
• Running differs from walking in that it eliminates double-limb support and introduces a float phase when neither foot touches the ground

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2. The Gait Cycle

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3. Subdivisions of the Gait Cycle

Stance Phase (60%)

Swing Phase (40%)

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4. Kinetics and Kinematics

• Hip: ~30° flexion at IC → extends to ~10° extension at TSt → 30°+ flexion during swing
• Knee: ~5° flexion at IC → 15-18° flexion at LR (shock absorption) → near-full extension at MSt → ~65° flexion in swing
• Ankle: ~5° plantar flexion at IC → 0° at neutral through MSt → ~10° dorsiflexion at TSt → ~20° plantar flexion at PSw/toe-off → returns to neutral during swing

Ground Reaction Force (GRF)

• The mean load-bearing vector that changes in magnitude and direction throughout the cycle
• It determines the moment/torque exerted on each joint
• During stance: GRF is anterior to the hip, posterior to the knee, and anterior to the ankle

Joint Loading

• Knee forces: 4-7x body weight during stance; 70% of load passes through the medial compartment
• During water walking: significant decrease in joint moments due to buoyancy

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5. Muscle Actions During Gait

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6. Determinants of Gait (6 Classic Determinants - Saunders/Inman)

1. Pelvic rotation - Pelvis externally rotates from IC to preswing, internally during preswing and swing; reduces total vertical displacement needed for limb advancement
2. Pelvic list (tilt) - Non-weight-bearing contralateral side drops 5°, reducing superior deviation of CoM
3. Knee flexion at loading - ~15° stance-phase knee flexion dampens impact at initial loading
4. Foot and ankle motion - Subtalar damping at LR; stability at midstance; propulsion efficiency at push-off
5. Knee motion - Works with foot/ankle to decrease unnecessary limb motion; flexes at IC, extends at MSt
6. Control of pelvic lateral displacement - ~5 cm motion over weight-bearing limb; narrows base of support, increases stance stability

• Vertical: sinusoidal curve
• Lateral: sinusoidal curve with amplitude of ~6 cm
• Body's CoM is located 2 cm anterior to S2
• Trunk's CoG is just anterior to T10 (~33 cm above hip joints in 184 cm individual)

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7. Pathologic Gait Patterns

Antalgic Gait

• Cause: Pain (hip/knee arthritis, stress fracture, infection)
• Mechanism: Patient shortens the stance phase on the painful limb to reduce load time; contralateral swing phase is more rapid
• Pattern: Dot-dash cadence (short stance, rapid swing); head dips on affected side

Trendelenburg Gait

• Cause: Weakness of hip abductors (gluteus medius); positive Trendelenburg sign = pelvis sags >2 cm during single-leg stance
• Mechanism: Failure to stabilize pelvis during single-limb support; pelvis drops on the unsupported (contralateral) side
• Pattern: Trunk lurches toward the affected side (compensated Trendelenburg = "waddling" if bilateral)
• Clinical associations: Superior gluteal nerve injury, polio, OA hip, total hip arthroplasty complications

High-Stepping / Steppage Gait (Foot Drop)

• Cause: Weakness of ankle dorsiflexors (tibialis anterior); common peroneal nerve palsy, L4/L5 root lesion
• Mechanism: Inability to clear foot during swing; exaggerated knee and hip flexion to clear foot from ground
• Pattern: Foot slaps ground at IC; hyperextension moment through knee in stance

Scissor Gait

• Cause: Overactive/spastic hip adductors (cerebral palsy, spastic diplegia)
• Mechanism: Adductor overactivity causes knees to cross midline; legs cross like scissors
• Pattern: Narrow base, knees crossing, typical in spastic CP; often combined with equinus

Crouch Gait

• Cause: Hamstring contracture, plantar flexor weakness, or cerebral palsy
• Mechanism: Excessive knee flexion throughout stance; increased dorsiflexion
• Pattern: "Crouching" posture; increased joint loading

Circumduction Gait

• Cause: Long limb, stiff knee, abductor shortening/overuse
• Mechanism: Swinging limb cannot flex normally, so patient circumducts it in an arc laterally to clear the floor

Hip Hiking Gait

• Cause: Long limb, stiff knee, hamstring weakness
• Mechanism: Elevation of pelvis on swing side to clear a stiff or long limb

Stiff / Ankylosed Hip Gait

• Cause: Hip arthrodesis or fusion
• Pattern: Head rocks to and fro; compensatory lumbosacral motion

Ataxic Gait

• Cause: Cerebellar pathology
• Pattern: Wide base, irregular cadence, lurching, incoordinated

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8. Gait Analysis Methods

Clinical Observation (Most Common)

• Watch patient walk from front, sides, and back
• Study one joint at a time: pelvis, hip, knee, ankle, foot
• Note stride length, cadence, rotational alignment, trunk position, and side-to-side differences

Quantitative Gait Analysis

• High-speed motion capture cameras from multiple angles
• Retroreflective markers aligned with palpable skeletal landmarks
• Force platforms (measure GRF)
• Kinematic data presented as 3D waveforms for each joint
• Electromyography (EMG) - documents muscle activation timing; identifies out-of-phase firing
• Pedobarography - plantar pressure/foot pressure mapping
• Oxygen consumption measurement (energy expenditure)

Quantitative gait analysis in preoperative planning for CP: when given to experienced observers after clinical recommendations were made, the surgical recommendation changed 52% of the time - Campbell's Operative Orthopaedics 15th Ed 2026.

Key Clinical Uses

• Preoperative planning in cerebral palsy and lower extremity surgery
• Postoperative outcome assessment
• Making further recommendations for bracing and physiotherapy
• Identifying gait deviations and muscle out-of-phase firing patterns

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9. Gait Abnormalities by Phase (Summary Table)

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10. Metabolic Cost of Gait

• Metabolic cost of walking increases with proximal-level amputations and is inversely proportional to the length of the residual limb and number of functional joints preserved
• Body weight is carried 70% by head, neck, trunk, and arms
• Trunk's CoG is ~33 cm above the hip joints
• Whole-body CoM is 2 cm anterior to S2

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• Miller's Review of Orthopaedics 9th Ed, Chapter 10 (Gait Biomechanics)
• Campbell's Operative Orthopaedics 15th Ed 2026, Gait Analysis Section
• Bailey and Love's Short Practice of Surgery 28th Ed, Table 35.1 (Types of limp)
• Imaging Anatomy: Bones, Joints, Vessels and Nerves (Thieme Atlas), Gait section