The aim of the study is to confirm the functional improvement obtained through treatment of spasticity on 2 agonist and antagonist muscles. The hypothesis is that treatment of both muscles gives a better and longer functional improvement than treatment of only one muscle. The target muscles are the rectus femoris and semitendinosus and the treatment is botulinum toxin. Clinical assessment (passive range of motion of the lower limbs, spasticity level, functional scales and subjective feeling) and gait analysis data (kinematics and kinetics data) are collected. Evaluations take place before treatment, 2 months and 6 months after treatment.