A 30-yr-old man with cauda equina syndrome resulting from a compression fracture of the L1 vertebra was enrolled in a rehabilitation program at the authors' hospital, and on completion, he was able to walk with the aid of an ankle-foot orthosis and cane. One year later, at his clinical follow-up visit, the patient complained of pain and swelling in his left knee. Despite the absence of a history of knee trauma, patellar subluxation was observed by physical examination. The patient then underwent several orthopedic surgeries to improve this condition. After this surgical process, a knee-ankle foot orthosis was prescribed to prevent any exacerbation of the knee lesion secondary to walking. Nonetheless, he again developed patellar subluxation 6 mos after his last surgery. There was no swelling of the knee or restriction of motion. Valgus stress test results were positive, and the medial knee was sensitive to palpation. Plain radiography showed a characteristic bony formation and calcification in the soft tissue next to the medial femoral condyle (Fig. 1). Pellegrini-Stieda disease was considered based on the characteristic x-ray findings and clinical course.
Radiographically, Pellegrini-Stieda disease seems as an ossification arising from the epicondylar portion of the medial femoral condyle.1 Humoral, neural, and local factors including tissue hypoxia, hypercalcemia, changes in sympathetic nerve activity, prolonged immobilization, and mobilization with frequent periods of exercise after prolonged immobilization may result in neurogenic ectopic bone formation.2
Although Pellegrini-Stieda disease has rarely been reported in patients with spinal cord injury,3 this report highlights the need for its consideration in the diagnosis of such patients if knee symptoms are present.
1. Niitsu M, Ikeda K, Iijima T, et al: MR imaging of Pellegrini-Stieda disease. Radiat Med
2. da Paz AC, Carod Artal FJ, Kalil RK: The function of proprioceptors in bone organization: A possible explanation for neurogenic heterotopic ossification in patients with neurological damage. Med Hypotheses
3. Altschuler EL, Bryce TN: Pellegrini-Stieda syndrome. N Engl J Med