We describe the case of a 58-year-old female patient. She refers to a hysterectomy at 42 years of age due to metrorrhagia secondary to fibroids. Two years earlier she had been assessed in gynaecology for lumbar densitometric osteoporosis (T-score at L1-L4 of -3, with normal figures in the femoral neck), treated with denosumab and vitamin D supplements. She reported no toxic habits, no personal or family history of fracture, and her BMI was normal. She consulted for mechanical pain in the left foot, of acute onset, without inflammation or triggering cause, which had been increasing in intensity until it became refractory to NSAIDs. On examination, there were no striking findings, except for pain on mobilisation of the left forefoot. No alterations in foot statics were observed. The patient provided a foot X-ray which showed no pathological findings. An MRI of the left foot was requested, which revealed a stress fracture in the 2nd MTT with periosteal callus and soft tissue oedema. An analytical study was performed, highlighting increased levels of PTH and vitamin D (103.7 pg/ml and 272 ng/ml, respectively), attributed to excess vitamin D supplementation. Renal function, serum and urinary calcium were normal. Treatment with vitamin D supplementation and denosumab was discontinued. The patient was assessed by the traumatology department and conservative treatment with unloading, relative rest, NSAIDs and magnet therapy was indicated, with progressive improvement. Due to the patient's age, 58 years, and the predominance of osteoporosis at lumbar level, she was considered a suitable candidate for treatment with SERMS (bazedoxifene), associated with calcium supplementation with vitamin D. One year later, in the same month in which she started with pain in the previous episode, she again reported the same symptoms in the left foot, with no triggering cause. An X-ray was requested which showed an old fracture callus in the 2nd MTT due to a previous stress fracture, with no other findings. An MRI of the left foot was performed to complete the study, which showed oedema of the 1st and 3rd MTT, of the cuneiform, scaphoid and talus bones, and tenosynovitis of the posterior tibialis. A new bone densitometry was requested, which showed a T-score in the lumbar spine of -3.5. The patient had not taken bazedoxifene and vitamin D continuously, so the importance of resuming them was insisted upon, given the bone mineral density figures, which had worsened. The fractures were treated with rehabilitation and unloading with progressive improvement.

Evaluating the case globally, we considered osteoporosis as a predisposing factor, as the patient was not obese, nor had she had trauma or other risk factors. The fact that the two episodes of pain began in the same month (coinciding with the change of season), a year apart, was striking. The patient did not report any change in her habits or physical activity (sedentary) at that time, so we believe that perhaps the change in the type of footwear may have led to an overload of the left foot, favouring the appearance of new stress fractures.

