Gait Analysis

1. Overview
Gait is the cyclical pattern beginning with initial contact of one foot and ending with the next initial contact of the same foot. It includes coordinated motion of the trunk, pelvis, hip, knee, and ankle.

2. Phases of Gait
• Stance Phase (60%): Foot in contact with ground.
  - Initial Contact: Heel strike.
  - Loading Response: Weight acceptance.
  - Midstance: Body progresses over the foot.
  - Terminal Stance: Heel rises.
  - Preswing: Toe-off preparation.
• Swing Phase (40%): Foot not in contact with ground.
  - Initial Swing: Foot lifted, forward acceleration.
  - Midswing: Tibia advances.
  - Terminal Swing: Preparation for initial contact.

3. Temporal Parameters (Cadence & Distance)
• Step Length: Distance between feet during double-limb support.
• Stride Length: Distance one limb travels in a full gait cycle.
• Step Time: Duration of one step.
• Cadence: Steps per minute.
• Walking Velocity: Distance traveled per unit time.
Children have a higher cadence and shorter step length than adults.

4. Neurologic Control of Gait
• Spinal cord reflexes guide early stepping.
• Supraspinal centers (motor cortex, cerebellum) control coordination and voluntary modulation.
• Neurologic disorders (e.g., CP, myelomeningocele) disrupt smoothness and adaptability of gait.

5. Function of Gait
• Efficient forward progression with minimal energy expenditure.
• Smooth transfer of body weight, allowing controlled forward fall.

6. Gait Energy
• Walking is inherently inefficient; energy is conserved by:
  - Minimizing vertical displacement of the center of gravity.
  - Coordinated muscle activity at hip, knee, and ankle.
• Physiologic Cost Index (PCI) measures efficiency (HR difference/walking speed).

7. Six Determinants of Gait
1. Pelvic rotation: Increases step length.
2. Pelvic tilt: Reduces vertical displacement.
3. Knee flexion during stance: Smoothens weight acceptance.
4. Foot and ankle motion: Controls forward progression (rockers).
5. Knee–ankle–foot motion coordination.
6. Lateral pelvic shift: Maintains balance.

8. Kinematics (Joint Angles)
• Sagittal Plane:
  - Hip: Flexion at IC → extension in stance → flexion in swing.
  - Knee: Flexion at IC → extension → peak flexion in swing.
  - Ankle: Plantarflexion at IC → dorsiflexion midstance → plantarflexion at push-off.
• Coronal Plane:
  - Pelvic obliquity allows limb clearance.
  - Hip abducts/adducts with weight shift.
• Transverse Plane:
  - Tibial external rotation; foot progression angle ~10–15° externally.

9. Muscle Activity
• Stance Phase:
  - Quadriceps control knee flexion during loading.
  - Gastrosoleus provides major power at terminal stance.
• Swing Phase:
  - Hip flexors initiate swing.
  - Tibialis anterior clears foot via dorsiflexion.
• Concentric contractions: Produce forward propulsion.
• Eccentric contractions: Control lowering and stabilize joints.

10. Kinetics
• Forces and moments across joints:
  - Ankle: Plantarflexion moment at push-off.
  - Hip: Power generation at terminal stance.
• Deviations in kinetics (weak calf, crouch gait) increase metabolic cost.

11. Pedobarography
• Measures plantar pressure distribution.
• Used for cavovarus, flatfoot, post-op correction evaluation.

12. Pathologic Gait
• Causes:
  - Weakness (e.g., CP, muscular dystrophy)
  - Contractures (e.g., arthrogryposis)
  - Spasticity or limb length discrepancy
• Common patterns:
  - Equinus gait, crouch gait, steppage gait, Trendelenburg gait.

13. Clinical Use of Gait Analysis
• Surgical planning (e.g., CP multilevel surgery)
• Assessment of orthotics and rehabilitation outcomes
• Video or laboratory gait analysis for objective parameters