An 83-year-old woman presented to the emergency department with a history of pain in the left hip of gradual onset over several days. There was no history of trauma and the X rays showed degenerative changes in the hip joint but no apparent fracture. She was sent home after being given reassurance, analgesics and a cane. Three weeks later she returned unable to mobilise after falling while getting out of bed and injuring the left hip. On this occasion the X-rays showed an acetabular fracture with femoral head protrusio. A CT scan confirmed the diagnosis and also demonstrated the absence of a haematoma in the surrounding soft tissues. The latter is characteristic of insufficiency fractures. Orthopaedic surgeons require a high index of suspicion for insufficiency fractures of the pelvis, femoral head and femoral neck in elderly osteoporotic patients who complain of hip pain without any history of trauma.