Fatigue fracture of the distal femur arising in the elderly.

Fatigue fractures most frequently involve the tibia and metatarsal bones in the young. We report a very unusual case of fatigue fracture in the distal femur of a 62-year-old man. The differential diagnosis was a pathological fracture due to a metastatic bone tumor. The diagnosis of fatigue fracture was based on the fact that the patient walked every day for a long time, together with the following radiological features: no definite cortical destruction, a radiolucent area surrounded by sclerosis on CT, no extraskeletal mass, and sharp linear low signal intensities in the center of the lesion on MR images. Rest and restricted walking improved his symptoms and fracture healing. Fatigue fracture should be ruled out even in the elderly, especially those who engage in sports activities for long periods.