Osteoid osteoma is a benign bone tumor. Benign means that it is not as aggressive as cancer. A bone infarct is just an island of dead bone, which doesn't cause much trouble. She may have twisted her leg or might have injured it unknowingly. The MRI findings may be incidental. If symptomatic treatment is not making her better, it is better to have a bone scan to see if the lesion is active or not. If it is not, there is usually no need for further intervention, except for periodic observation. If the lesion is active, it may be necessary to currete (remove) the lesion through surgery. However, the decision has to be from the orthopaedic surgeon who is taking care of her, based on history, physical examination and judgement.