[Reactions of the overlapping volo-ulnar margin of the ulnar head in chronic polyarthritis--a hitherto disregarded sign].

The volo-ulnar margin of the ulnar head is mostly superimposed by the base of the ulnar styloid, but often remains visible as a contour. The ulnar head is surrounded by the radio-ulnar synovial compartment. At the wrist this compartment is one of the most often affected synovial compartments in rheumatoid arthritis. Therefore reactions often occur at this margin in rheumatoid arthritis with thinning, reactive sclerosis and erosion. These reactions occur as often as the erosions at the neighbouring ulnar styloid.