1. There is an increasing prevalence in the evidence of prenatal extended knee postures in the legs of newborn, from normal births to breech deliveries and to babies with hip displacements. The extended knee postures are also commoner in female births. 2. Babies with reducible hip displacements appear to be born more often in summer as the result of winter conceptions. Spontaneous recovery is very high, with or without splintage. 3. Irreducible hip displacement does not respond to splintage during the first six months of life. Even with adductor tenotomy, there is a great risk of acetabular and femoral epiphysial damage. This is thought to be due to incarceration of the limbus, present at birth.