Impaired growth at one end of a long bone may be compensated by increased growth at the intact end. In experiments, such a compensatory growth was less frequently observed in the cartilaginous structures of the skull than in the sutures. Achondroplasia is an example of compensatory growth in the neurocranium, the disturbed growth of the base of the skull being compensated by an increase of the calvarium according to the space required by the contents of the cranial cavity. In the face, compensatory changes may be observed in conjunction with increased adenoids, as a result of impaired growth of the mandible in case of juvenile rheumatic arthritis or in conjunction with condylar fractures in young age. The processes of growth during orthodontic treatment constitute the border-area between compensatory and adaptive growth.