[Diagnostic approach and differential diagnosis of mon- and oligoarthritis].

Reasons of mon- and oligoarthritis are heterogeneous. The diagnostic approach includes a detailed medical anamnesis, physical examination and imaging (conventional X-ray, sonography, MRI and, CT). Analysis of the synovial fluid is required in suspected septic arthritis and frequently helps in diagnosis and differential diagnosis of crystal arthropathies. Dual-energy-CT (DECT) detects sodium urate crystals and can replace joint puncture in some cases. In addition to crystal arthropathies and septic arthritis, differential diagnosis of mon-/oligoarthritis includes reactive arthritis, arthrosis and monarthritic courses of SpA/PsA. A rheumatologist should be consulted particularly in the case of persistent monarthritides, in order to initiate a specific therapy to prevent secondary damage.