Abstract Introduction 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. Problem Assessment of these patients, in order to establish their diagnosis, is challenging, due to the range and complexity of their clinical presentation. Rationale 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. Objective 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. Result 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. Discussion The five main groups of differential diagnoses are discussed in detail.