1. A satisfactory procedure for oxygen pneumo-arthrography is presented which has been used in 508 examinations of the knee.
2. The four steps in the procedure are outlined.
3. The complicated anatomy of the lateral meniscus is emphasized and demonstrated by Figures 4 and 5.
4. The difficult interpretation of the various shadows involving the lateral meniscus is discussed.
5. A general outline for interpretation of pneumo-arthrographic findings is presented.
6. Fourteen cases in which operations were performed are described to show a variety of lesions in which the pneumarthrograms have been of value.
7. A plea is made for the necessity of perfect technique in this procedure to prevent disappointing results.