Purpose of review: Describe why this review is timely and relevant. Identifying monosodium urate (MSU) and calcium pyrophosphate dehydrate (CPPD) crystals allows a quick and definitive diagnosis of both gout and CPPD arthritis, and remains the accepted gold standard. These diseases are still often diagnosed on inaccurate clinical grounds. Crystal identification has received little critical attention since its introduction, and it appears necessary to review the technique paying special attention to the possible reasons which deter clinicians.
Recent findings: Describe the main themes in the literature covered by the article. Synovial fluid analysis for crystals is a simple procedure allowing immediate and definite diagnosis of gout and CPPD arthritis when clinics are fitted with a proper microscope and the rheumatologists appropriately trained. This review also illustrates how crystal analysis in synovial fluid can be initially approached with both the widely available ordinary light microscope and a simple polarized one and with good results.
Summary: This study describes the implications of the findings for clinical practice or research. We hope that those not performing synovial fluid analysis will be stimulated to acquire or perfect the technique and obtain a compensated polarized microscope to comply with current standards.