Odds

You see a 40 year old woman in clinic who complains of pain at the bottom of her left foot. She says "I've been trying distance running and ballet to cut down on my weight." Her BMI is 30. On exam you do the following:

This elicits point tenderness. You get a screening complete blood count, basic metabolic panel, erythrocyte sedimentation rate, and C-reactive protein which are all within the normal range. X-rays are shown below (and labeled!):

Challenge: This could be many things, but what is the most likely cause?

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