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.

1. A case is reported of a Jamaican boy of fifteen months with typical and florid manifestations of dysplasia epiphysialis hemimelica associated with a number of atypical features not previously recorded.

2. The progress of the disorder over a limited period of two years is described and the development of the atypical features is discussed.

1. Breech malposition and hormonal joint laxity produce atraumatic posterior dislocations in the hip joints of young rabbits.

2. Experimental studies were shown to cause the development of a limbus and other softtissue changes similar to those found in human congenital dislocations.

3. The development of femoral retroversion and anteversion in the presence of joint laxity is described.

4. The co-existence of breech malposition and hormonal joint laxity in utero, and their importance as prime factors in the etiology of congenital dislocation of the hip, are discussed.

1. Sustained medial rotation of the hind limb in the immature rabbit produces femoral anteversion and acetabular dysplasia.

2. Sustained lateral rotation produces retroversion.

3. Splinting the hind limbs in the Lorenz position corrects both anteversion and retroversion.

4. The mechanism of the Lorenz position is discussed.