Step 1: A scissoring walk happens when the thighs are pulled toward the midline so the knees and ankles touch or cross while walking. The driver is hypertonic hip adductors.
Step 2: Such hypertonia is a feature of upper motor neuron (pyramidal) damage, which causes spasticity rather than weakness with low tone.
Step 3: The textbook condition with this spastic adductor pattern is cerebral palsy, particularly the spastic diplegic form, where chronic UMN injury fixes the legs in adduction.
Step 4: Polio gives flaccid LMN paralysis, and electrolyte or bilirubin disturbances do not cause this fixed spastic gait, so they are excluded.
\[\boxed{\text{Cerebral palsy}}\]