[Arthritis in adolescence].

Joint problems in adolescence are often monoarticular. In the acute form the differentiation between trauma and infection is of utmost importance, whereas in chronic joint diseases the differentiation will be mainly between mechanical disorders and true rheumatic diseases. In pauci- or polyarticular arthritis of short duration viral infections have to be considered, since true rheumatic diseases tend to run a more chronic course. In girls true sero-positive juvenile rheumatoid arthritis typically appears in this age group. In adolescent boys seronegative Spondylarthropathies involving the lower extremities and not uncommonly with enthesopathies may occur. The typical involvement of the sacro-iliac-joint usually starts after the age of 18 years. Bacterial arthritides are predominantly monoarticular and are caused in more than 50% by staphylococci.