Differential diagnosis in variants or abnormalities of the hip on MRI.

In the differential diagnosis of unspecific hip pain MRI becomes increasingly important. In particular it is useful in the diagnosis of avascular necrosis, primary and secondary bone tumors, osteomyelitis and synovial processes. According to the higher frequence of MR examinations of the hip the number of nonpathological incidental findings is rising. 39 'pitfalls' and abnormalities were found on MRI of 152 patients with unspecific hip pain. Soft tissue penetrating cortical lesions of the femoral neck (herniation pit, n = 4), physiological changes of bone marrow, synovial proliferation (n = 6) of the hip joint capsule, epiphyseal scars of the femoral head (n = 12) and the transient osteoporosis (n = 12) are some of the morphological changes of the hip, which may cause difficulties and misinterpretations on MRI of the hip. Knowledge of their radiological characteristics on MRI is important, especially in cases of unspecific hip pain.