Left foot pain

A 17-year-old adolescent appears with 8-week-old left foot pain. She is a runner who had a radiograph three weeks ago that revealed a modest periosteal response around the distal third metatarsal (Figure 1). Figure 2 shows considerable callus formation around the distal third metatarsal on a second radiograph taken in the office. On physical examination, the patient shows modest discomfort to palpation over the distal third metatarsal. The patient is concerned about the cause of his stress fracture.