Leg movements in the supine position of 49 infants with spastic diplegia (three 
to 11 months corrected age) were examined. Only simultaneous flexion and 
extension of the hips and knees were seen, with exceptional isolated hip 
movements; the simultaneous movements had synergic features. When the knees were 
flexed, the hips were flexed, abducted and externally rotated, and the ankles 
were dorsiflexed. When the knees were extended, the hips were extended, adducted 
and internally rotated and the ankles were plantar-flexed. Hip flexion combined 
with knee extension (leg elevation) and isolated knee movements were not seen in 
diplegic infants, but were seen in all control preterm infants with a good 
prognosis, after five and six months corrected age, respectively. The absence of 
these movements is a useful diagnostic item for spastic diplegia.