The lengths of the ilium and ischium and their angles relative to the acetabulum are functionally important.

http://en.wikipedia.org/wiki/Pelvis

 In ambulatory mammals the acetabula are shallow and open to allow a wider range of hip movements, including significant abduction, than in cursorial mammals. The lengths of the ilium and ischium and their angles relative to the acetabulum are functionally important as they determine the moment arms for the hip extensor muscles that provide momentum during locomotion.