Low-grade chondrosarcoma in 50-year-old woman who had progressive right knee pain. A, Anteroposterior radiograph of the right knee shows expansile lesion in proximal fibula. Lesion appears to contain calcification suggesting cartilaginous lesion. B, Coronal T1-weighted MR image shows that lesion remains entirely within cortex. C, Primary resection was done without biopsy. This treatment strategy allowed for wide margins without contamination of common peroneal nerve (arrow). D, Lesion proved to be low-grade chondrosarcoma. E, Radiograph after primary resection of proximal fibula.