How often should the hips be evaluated in children with cerebral palsy?

The frequency of hip screening in children with cerebral palsy varies depending on their level of involvement, age, and preexisting level of hip involvement. In general, children who can ambulate without assistive devices require less frequent screening than children who rely on wheelchairs for ambulation. The level of involvement in children with cerebral palsy is reported mostly by GMFCS level(Growth Motor Function Classification System). The level is measured by the physical ability of the child and higher GMFCS level indicates a higher the level of involvement. The GMFCS is usuallly stable through the child's growth and development.
Currently the best guidelines for the frequency of hip screening in children with cerebral palsy is published by the Australian Academy of Cerberal palsy and Developmental Medicine. The implementation of these guidelines has been very helpful in preventing hip pathology in children in Australia and Europe.  I believe these guidelines should be implemented in the care of all children with cerebral palsy.

Australian guidelines for hip screening in children with cerebral palsy