Pediatric Cerebral Palsy Gait Patterns

Gait Pattern

Pattern severity 40%

Cadence 90 steps/min

Live Readouts

Knee flexion, midstance

5.0°

Hip adduction, stance

0.0°

Ankle @ heel strike

0.0°

Gait cycle phase

Crouch index (0 = upright, 1 = severe crouch)

0.10

How it works

Each leg's hip, knee and ankle flexion angle is driven by an idealized joint-angle curve θ(t) over the gait cycle t ∈ [0,1) (t = 0 at heel strike, t ≈ 0.6 at toe-off, t = 1 back to heel strike), built from key-frame control points taken from typical clinical gait-analysis traces and interpolated with cosine easing:

θ(t) = lerp_cos( θᵢ, θᵢ₊₁, (t − tᵢ)/(tᵢ₊₁ − tᵢ) )   for tᵢ ≤ t < tᵢ₊₁
lerp_cos(a,b,u) = a + (b−a)·(1 − cos(πu))/2

The left leg uses phase t, the right leg uses phase (t + 0.5) mod 1 — a 50%-offset walking gait. Three cerebral-palsy patterns are modeled as parametrized deviations from the typical curve, scaled by a severity s ∈ [0,1]:

Crouch:     knee(t) += 35°·s   (persistent stance flexion — never fully extends)
            hip(t)  += 18°·s ,  ankle(t) += 12°·s (excess dorsiflexion)
Scissoring: hip_adduction(t) = 22°·s·sin²(πt)   (thighs cross toward midline in stance)
Toe-walk:   ankle(t) −= 30°·s  for t < 0.5   (equinus / early plantarflexion, no heel strike)

Knee flexion at midstance and hip adduction at mid-stance are the two angles orthopedists watch most closely on a real gait lab printout — they distinguish crouch gait (chronically bent knees, often from spastic hamstrings/hip flexors) from scissoring gait (spastic hip adductors pulling the legs together, sometimes causing them to cross). Toe-walking (equinus) reflects spastic/short gastrocnemius-soleus preventing heel strike. The crouch index is a simple 0–1 composite of knee + hip flexion deviation from the typical curve, used clinically as a rough severity proxy before a full instrumented gait analysis.

This is a simplified educational model, not patient-specific clinical data — real gait analysis uses motion capture and force plates to measure these curves directly.

Right leg Left leg

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