We examined 50 patients with diastrophic dysplasia both clinically and radiologically. Two legally aborted fetuses were dissected. The mean age of the patients was 16.2 years (newborn to 38) and the mean follow-up was 11.4 years (3 months to 34 years).

The fetal hips and MRI of newborn infants showed congruity and no significant joint deformity. Flexion contracture of the hip became evident later in 93% and was progressive. The radiological appearance of the proximal femoral ossific nuclei was delayed and in 17% of males and 28% of females the ossific nuclei had not appeared by the age of 12 years.

Radiological measurements differed considerably from reference values and were related to the rapid and progressive restriction of rotational movement and the increase in flexion contracture. The typical findings were flattening and inferomedial bulking of the femoral head and a double-hump deformation. The changes in the hip led to secondary osteoarthritis before early middle age. We describe the clinical and radiological measurements which define the early degeneration of the joint.

The exceptionally high prevalence of diastrophic dysplasia in Finland has enabled us to analyse the foot deformities of 102 patients at their first orthopaedic evaluation and classify 204 feet into five categories. The most common finding (43%) was a foot with tarsal valgus deformity and metatarsus adductus; 37% showed either equinovarus adductus (29%) or equinus (8%) deformities. At the first examination 13% showed metatarsus adductus deformity alone, and 7% were clinically normal. The expression 'club foot', generally used for the foot deformity in diastrophic dysplasia is a misnomer. There is a wide spectrum of deformities, some of them specific for the condition.