Unusual stress fracture of the femoral neck in a young adult not caused by excessive stress: a case report.

A 30-year-old man complained of a 10-day history of gradual onset of severe left leg pain. He did not have any history of trauma or excessive training. Routine laboratory data showed no abnormal findings. He was able to perform passive motions of the hip joint without pain, but active motion of the left hip joint was impossible due to anterolateral thigh pain. Plain radiographs of the hip showed no abnormal findings. However, bone scintigraphy indicated trace accumulation in the left femoral neck, and T(1)-weighted magnetic resonance imaging showed a linear low signal on the inferomedial aspect of the femoral neck. Bone mineral density of the lumbar spine was 1.053 g/cm(2), which ruled out osteoporosis. The thigh pain was resolved 2 months after onset with conservative treatment, when plain radiographs showed sclerotic change and a reduction in the intensity of the low signal of T(1)-weighted magnetic resonance imaging. Our diagnosis of unusual stress fracture indicates that the possibility of stress fractures without bone fragility should be kept in mind when young adults complain of atypical pain even without evidence of unusual activities.