1. Luetic synovitis of the knee, especially in children, is very often erroneously diagnosed, as roentgen-ray examinations are negative.
2. In chronic hydrops of the knees with a negative roentgen-ray report, it is important to do a Wassermann on the joint fluid as well as on the blood.
3. The history of trauma does not-rule out the possibility of lues, for the two may be associated.
4. Since luetic Synovitis, before bone involvement, responds quickly to antiluetic treatment, an early diagnosis is essential.