Knee joint injury by mercury from a broken thermometer: case report and review of the literature.

An 11-year-old boy injured the inner side of his left knee when accidentally breaking a mercury thermometer. He immediately developed an acute synovitis. Soft tissues and synovium containing metallic mercury droplets were completely removed at operation. The patient recovered within five weeks. Symptoms and signs of acute or chronic mercury poisoning were not observed. However, because injury by a mercury thermometer may become very serious if the metal is absorbed by the tissues and disseminated through the circulatory system, immediate local excision of tissue is necessary. Interestingly, the histologic appearance of the synovial membrane was remarkable by the lack of any foreign body giant cell reaction.