44 patients with familial short stature scheduled for bilateral femoral distraction osteogenesis with intramedullary lengthening nails were randomized to one leg administered botulinum toxin type A within the muscles of the thigh, and one leg administered placebo in a similar manner. The aim of this study was to evaluate the effects of botulinum toxin type A injection during femoral distraction osteogenesis on adjacent joint ROM and distraction-induced pain. Patients were assessed for pain, knee extension and hip flexion contracture, maximal thigh circumference, and the incidence of injection-related adverse events during the distraction and consolidation phases. No significant differences between groups for outcomes were observed.