Summary: The effect of surgical lengthening of the gastrocnemius fascia on ankle joint kinematics and kinetics during gait in patients with cerebral palsy (CP) was evaluated. Twenty independent ambulators (24 sides) were included in this retrospective study. The evaluation included clinical examination, calculation of joint kinematics and kinetics, and collection of surface electromyography (EMG) during gait. Postoperative improvements were noted in static heelcord range of motion (ROM), with an associated increase in dorsiflexion in stance and swing. Kinetic analysis showed a decrease in the abnormal energy generated around the ankle in midstance and a statistically significant increase in the energy generated in late stance for push-off.