A bone dysplasia is often a difficult diagnosis for the radiologist to achieve. However, principles of interpretation can make the task both interesting and often straightforward. In general, one of the factors of bone growth is in some way impaired, yielding an abnormal skeleton. To analyse what is impaired may greatly assist in narrowing the diagnostic possibilities. In most dysplasias, the affected growth factor is either one of enchondral or membranous bone growth. When interpreting bone radiographs for dysplasia one should be aware that aberrant positioning, that may lead to foreshortening in space, may simulate impaired growth in time. Dysplasia diagnosis for the paediatric radiologist is an art, but it can also be a science (as well as a pattern recognition challenge).