Giant-cell tumor of the patella.

We report a 38-year old man with a giant-cell tumor in a rare site, the patella. Primary patellar neoplasms are highly unusual. According to a survey by the Bone and Soft Tissue Tumor Committee of the Japanese Orthopaedic Association, of more than 2,126 giant-cell tumors of bone reported since 1972, only 22 were primary patellar neoplasms. We present a case of this rare entity along with its clinical and radiographic features. The first clinical symptom was anterior knee pain. Though anterior knee pain has numerous and varied causes, it is necessary to consider patellar bone tumors in the differential diagnosis.