The W-sit position describes the shape the legs make in the sitting position. The knees are turned in and the bottom rests between the two feet. The opposite position is called Indian or tailor-sitting. This alternate position turns the hips and knees out with the ankles crossed in front.
In young children, the hipbones and joint are still unformed with rubbery cartilage in the hip socket. The top of the thighbone (femur) fits into the hip socket to form the hip joint. The hip is more likely to dislocate if the femur is twisted at the top.
This slight twist is called torsion. A torsion forward is an anteversion. A twist in the opposite direction is called retroversion. Sitting for long periods of time in the W-sit position can cause anteversion. In some children, this can lead to hip dislocation.