Fig. 5

Illustration of the hip joint explaining why ischio-femoral impingement (IFI) symptoms are more common than femoro-acetabular (FAI) symptoms in hips with multiple hereditary (MHE). a The normal hip joint morphology without MHE. The hatched part in the figure shows the exostoses that can occur in the femoral head and neck area. In this circumstance, the incidence of both FAI and IFI is likely to increase. b MHE hip patients with the characteristic deformities. Though hatched part of the exostoses may increase the possibility of the impingement, coxa valga deformity reduces the possibility of impingement between the femoral head and acetabulum by increasing the working distance. On the contrary, coxa valga deformity acts as a risk factor for the development of IFI reducing the distance between the exostoses and the ischium