Pathologic hip (classified as subluxated) examined with ultrasound the first week after birth. The dotted circle indicates the femoral head and the dotted horizontal line indicates the level of the lateral acetabular margin. Distance a is measured central in the femoral head from the level of the lateral acetabular margin to the acetabular floor (blue line). Distance b represents the diameter of the femoral head and is measured from the lateral joint capsule which equalizes the lateral part of the femoral head to the acetabular floor (white line). The femoral head coverage (FHC) is presented in %: (FHC = a / b × 100 = 33%). Red arrow points at the lateral acetabular margin, blue arrow points at the acetabular floor, whereas the white arrow points at the lateral joint capsule.Fn: femoral neck; IL: os ilium.