A review of 587 knee arthrographies revealed filling of lymph vessels in 12 cases. They occurred in connection with arthritis (4 rheumatoid), osteoarthritis, ruptured meniscus, ruptured popliteal cyst and after operation. Lymphatic filling was not related to the leakage of contrast through a ruptured popliteal cyst or to inadvertent extra-articular injection. Filling of lymphatics is more likely to occur in examinations with a positive contrast medium when a larger amount of medium is used.