Sequential multiple insufficiency fractures around knee over 6 months in a patient with primary osteoporosis

In this report, we describe a case of multiple insufficiency fractures occurring over 6 months in the bilateral knees of an individual with primary osteoporosis. An 87-year-old woman complained of spontaneous pain in her right knee. A plain X-ray did not show any lesions at the time; however, 2 weeks later, a slightly displaced supracondylar fracture was observed. The fracture was treated with a long leg cast for 6 weeks. The patient was able to walk with a walker 12 weeks after the injury, but her right thigh muscles had atrophied. Four months after the first injury, she suffered left knee pain. Magnetic resonance imaging (MRI) showed an undisplaced supracondylar fracture of the left femur. After undergoing the same treatment as for the previous fracture for 8 weeks, she complained of pain in the proximal tibia, and a fracture in the lateral tibial plateau was observed by MRI. No malignancy or endocrine disorders were found by imaging or laboratory studies. Her bone mineral density was found to be low, and she was diagnosed with multiple insufficiency fractures due to primary osteoporosis. The work overload on the healthy side induced by muscle weakness on the affected side may have caused the subsequent insufficiency fractures on the healthy side. These findings suggest that one should pay attention to and treat lower limb muscle atrophy when managing insufficiency fractures of the lower limbs.