Non traumatic dislocation of the patella in children: the case for a dysplastic aetiology.

Congenital dislocation of the patella may be a phenotype, which has several genotypes, i.e. it may be congenital or acquired. This hypothesis is suggested with three illustrative case studies. Risk factors predictive of the development of irreducible dislocation of the patella in infancy are suggested. As there is a spectrum of possible aetiologies, 'late' diagnosis and a number of 'risk' factors but a common pathology, the word 'congenital' is not always appropriate. We suggest 'Developmental dysplasia and dislocation of the patella (DDDP)' is a more appropriate term for this rare condition.