[Early diagnosis of Lyme arthritis].

Lyme-Arthritis is one of the most frequent manifestations of Lyme disease. Transient arthritides may already develop in the early disease stage. However, typical Lyme arthritis manifests weeks to months after the infection as intermittent mon- or oligoarthritis predominantly affecting the knees. Massive knee effusions may lead to popliteal cysts that often rupture. Chronic arthritides are rare. The diagnosis of Lyme arthritis mainly is based on clinical grounds and confirmed by laboratory tests. Direct detection of the causing agent by culture is difficult and not suitable for clinical use. With polymerase chain reaction based assays in up to 80% of untreated patients with Lyme arthritis B. burgdorferi DNA can be detected in joint fluid or synovial membrane specimens. While this method is not widely available yet it will become a routine diagnostic tool in Lyme arthritis in the near future. Borrelia serology is still the most important laboratory test. A negative serology almost certainly rules out Lyme arthritis. A positive serology alone, however, does not proof Lyme disease and must be critically interpreted in context with clinical symptoms.