A 73-year-old man presented with a chief complaint of progressive left knee pain for two months. He had a history of total thyroidectomy and central lymph node dissection due to papillary thyroid carcinoma three months ago. MRI images revealed a solid mass in the left patella. A solid mass demonstrated low signal on T1 weighed image, and high signal on T2 weighed image. And whole body bone scan showed focal photon defect in same lesion of left patella. The histologic result of left knee lesion was adenocarcinoma, consistent with metastatic papillary thyroid carcinoma. Although patellar metastasis of papillary thyroid carcinoma is very rare, when knee pain and radiologic abnormality are noted, differential diagnosis of metastasis is necessary.