Suggest Treatment For Displaced Knee Caps

My child has had both knee caps displaced? His legs appear to be bowed as well. We go to a sports medicine clinic and the right knee cap is fine so far (it was displaced on Nov. 20th. The left knee cap displaced on Dec. 28th. The foot doctor says he has high arches but that orthodics will not cure the knee cap issue and did not cause it. He has been told to strengthen the inner leg muscles and stretch the outer muscles (I.T. bands).