ANSWER
The radiograph shows a right knee prosthesis in place with no evidence of failure or displacement. Of note, there is a hyperdense, somewhat elongated lesion along the distal third of the femur. Radiographically, this is most likely consistent with an enchondroma. Enchondromas are typically benign bone lesions that originate from cartilage. They seldom cause pain and are usually found incidentally. No specific treatment is warranted.
The patient was referred to his orthopedist for follow-up.