The aim of the study is to highlight the skeletal changes that result from untreated DDH if it is decided to leave the hip unreduced, as may occur if a child presents at a late age. This is of interest today as the data with which we try to determine prognosis in such cases is very old and comprised of small patients numbers. The method used is the study of c.10,000 human skeletons excavated from the medieval cemetery of Spitalfields in London, dating from 1100–1530AD. Diagnosis was made by the presence of an abnormal true acetabulum incompatible with articulation with a femoral head in life, with an associated false acetabulum on the iliac wing. The results demonstrated a range of skeletal consequences in the 13 dislocated hips present. At the hip joint itself, degenerative change was only present in cases with a well developed, cup-shaped false acetabulum. Only 17% of cases had such a cup-shaped false acetabulum. Cases with no such false acetabular cup (83%), presumably with soft tissue articulation, showed no degenerative change. Hip adduction with valgus knee was common, as was femoral neck anteversion with compensatory tibial torsion. Scoliosis in unilateral cases caused lateral wedging of vertebral bodies and markedly asymmetric degenerative change in older individuals. We conclude that the presence or absence of a deep cup-shaped bony acetabulum at late presentation may have prognostic implications as to whether degenerative change in the hip, and so pain, may occur in adulthood. If confirmed by clinical studies, this may influence whether an attempt at reduction should be made. From the viewpoint of the spine, if a hip is reduced late, surgeons should be aware that the scoliosis may not correct as they would expect if the vertebrae are already laterally wedged by the time the child presents.