Increase in the magnitude of lengthening during the limb lengthening procedure involves a high risk of decreased range of motion (ROM) in adjacent joints. Even though patients with achondroplasia can tolerate a relatively larger amount of lengthening owing to its inherent soft-tissue laxity, they often exhibit significant joint contractures during extensive lengthening. In the present study, we evaluated temporal changes in the ROM of the hip, knee, and ankle joints throughout the treatment period in 12 limbs of six patients with achondroplasia who had undergone extensive tibial lengthening. The ROM of hip extension, knee extension, and ankle dorsiflexion were measured before distraction, at every 1-cm length gained during distraction, and at monthly intervals after the termination of distraction until the frame removal. The average amount of lengthening was 9.2±1.2 cm, corresponding to 52.8±6.8% of the original bone length. Equinus deformity of the ankle was observed in the early phase of distraction, whereas flexion contracture of the knee and hip appeared in the middle and the late phase of distraction, respectively. With dedicated physiotherapy and deliberate orthosis wearing, all of the contracture gradually resolved up to the preoperative state after the termination of distraction. This is the first report showing the development of contracture in the hip, a nonadjacent joint for the tibial lengthening.