I can surely understand how upset you must be about this.  The condition is congenital and diagnosed by examination.  One would think that if you noticed it the physician should have too and at the very least sent you to an orthopedist way back when.  I would consult a med mal attorney in your area asap. If his or her actions deviated from the normal standard of care and as a result your child must now go through a much more difficult course of treatment because he or she is older I think you have a good shot.  Good luck.