Skeletal dysplasia is the result of abnormalities of bone and cartilage development. Under the skeletal dysplasia ‘umbrella’ there are over one hundred individual conditions, which may present primarily or as a consequence of secondary complications.Assessment of these patients, in order to establish their diagnosis, is challenging, due to the range and complexity of their clinical presentation.A complete assessment includes a careful history, examination, radiological imaging, baseline blood tests and genetic investigation. This should lead to a definitive diagnosis, however, this may not be feasible immediately, especially in an FRCS examination scenario.A helpful approach would be to provide a structured, clear and concise system of assessment which leads to a reasonable differential diagnosis; an explanation can then be given to the patient or the examiner, and further tests can be recommended.We have designed a pragmatic diagnostic sieve, which guides the user through a series of logical, structured questions and observations in order to achieve a diagnosis.The five main groups of differential diagnoses are discussed in detail.