Patellar metastasis from primary tumor.

Although bone tumors are frequently located in the knee area, primary tumors of the patella are rare and patellar metastases are even rarer. Knee pain is the most common complaint of patients with patellar metastases. Owing to the low incidence of patellar metastases, misdiagnosis is not unusual. The present review analyzes ~44 cases of patellar metastases originating from distinct primary sites. Reports of malignant tumors of the lung and kidney metastasizing to the patella were more common than those of other patellar metastases. Relative incidence, symptomatology, imaging features, histopathology and treatment options for these patellar metastatic lesions are described respectively along with a review of the literature. Despite numerous experiments demonstrating the reasons for implantation of tumor in patella, the answer to this question has not yet been revealed. In the light of the increasing attention on the diagnosis and the treatment of these lesions, the availability of the integrated information regarding metastases in the patella becomes more relevant.