I would take it to mean that the ball is sat in the socket but the socket is not yet as deep as they would like. Depending on the measurements they might say they just need to keep an eye on them - or suggest a brace (as the positioning of the ball into the socket encourages the correct growth - this is why breech babies are prone to HD as often their feet are more together so the hip angle hasn't encouraged the correct development - same can happen with bigger babies - and with girls they think is linked to them having receptors for the relaxin hormone their mothers produce during pregnancy - so that relaxes their muscles/ligaments so doesn't hold the ball into the socket to encourage the correct growth).
Bookmarks