Acetabular fractures in the elderly are increasingly common; however, an antecedent of trauma may not be known, and the diagnosis easily missed. Early identification and prompt management are needed in order to minimise morbidity rates, but little has been published on occult acetabular fracture.In this paper we present three cases of occult acetabular fracture in patients older than 75 years. All three are females and had previously been operated on the ipsilateral hip with an implant (two proximal femur fractures treated with a proximal intramedullary femoral nail, and one case of total joint replacement); these acetabular fractures could be related to the existence of a stress shielding mechanism.We believe that whenever an elderly patient feels groin pain, and anteroposterior pelvis X-rays are normal, oblique Judet projections (obturator and iliac) should be obtained. In any case, displacement will make any fracture evident within a few weeks.