Synovial fluid analysis
- Dalton E Sholter, MD, FRCPC
Dalton E Sholter, MD, FRCPC
- Associate Clinical Professor of Medicine
- University of Alberta
- Anthony S Russell, MD, FRCPC
Anthony S Russell, MD, FRCPC
- Professor of Medicine
- University of Alberta
- Section Editors
- Robert H Shmerling, MD
Robert H Shmerling, MD
- Section Editor — Diagnostic Issues in Rheumatology
- Associate Professor of Medicine
- Harvard Medical School
- Stephen B Calderwood, MD
Stephen B Calderwood, MD
- Editor-in-Chief — Infectious Diseases
- Section Editor — Bacterial Infections
- Professor of Medicine (Microbiology and Immunobiology)
- Harvard Medical School
Synovial fluid analysis is helpful for determining the underlying cause of arthritis, particularly for septic or crystal-induced arthritis. The white cell count, differential count, cultures, Gram stain, and crystal search using polarized light microscopy are the most useful studies. An overview of synovial fluid analysis in the native joint is discussed here. Septic arthritis, prosthetic joint infections, gonococcal arthritis, and fungal and mycobacterial arthritis are discussed in detail separately. (See "Septic arthritis in adults" and "Prosthetic joint infection: Epidemiology, clinical manifestations, and diagnosis" and "Prosthetic joint infections: Treatment" and "Disseminated gonococcal infection" and "Skeletal tuberculosis".)
Arthrocentesis with synovial fluid analysis should be attempted in all patients who have a joint effusion or signs suggestive of inflammation within the joint, without a known cause. The most important reason to perform a synovial fluid analysis is to evaluate for septic arthritis in a patient presenting with an acutely swollen joint that is painful and warm. (See "Septic arthritis in adults".)
Synovial fluid analysis is also particularly important for definitively diagnosing gout or pseudogout. In combination with a negative Gram stain and bacterial cultures, a diagnosis of gout or pseudogout may be established by confirming the presence of crystals of monosodium urate (MSU) or calcium pyrophosphate dihydrate (CPPD) in a patient presenting with unexplained inflammatory arthritis. (See "Clinical manifestations and diagnosis of gout" and "Clinical manifestations and diagnosis of calcium pyrophosphate crystal deposition (CPPD) disease".)
Synovial fluid analysis is also helpful in narrowing the differential diagnosis by distinguishing between categories of joint effusions (ie, inflammatory versus noninflammatory) (table 1), and to diagnose hemarthrosis (algorithm 1). (See 'Categories of joint effusions' below.)
CATEGORIES OF JOINT EFFUSIONS
Results of synovial fluid analysis can be used to categorize the fluid as noninflammatory, inflammatory, septic, or hemorrhagic based upon the clinical and laboratory analysis (table 2).
- McCutchan HJ, Fisher RC. Synovial leukocytosis in infectious arthritis. Clin Orthop Relat Res 1990; :226.
- Baron EJ, Miller JM, Weinstein MP, et al. Executive summary: a guide to utilization of the microbiology laboratory for diagnosis of infectious diseases: 2013 recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM)(a). Clin Infect Dis 2013; 57:485.
- Freemont AJ. Microscopic analysis of synovial fluid--the perfect diagnostic test? Ann Rheum Dis 1996; 55:695.
- Clayburne G, Baker DG, Schumacher HR Jr. Estimated synovial fluid leukocyte numbers on wet drop preparations as a potential substitute for actual leukocyte counts. J Rheumatol 1992; 19:60.
- Kerolus G, Clayburne G, Schumacher HR Jr. Is it mandatory to examine synovial fluids promptly after arthrocentesis? Arthritis Rheum 1989; 32:271.
- Dieppe P, Swan A. Identification of crystals in synovial fluid. Ann Rheum Dis 1999; 58:261.
- Chen LX, Clayburne G, Schumacher HR. Update on identification of pathogenic crystals in joint fluid. Curr Rheumatol Rep 2004; 6:217.
- Goldenberg DL, Reed JI. Bacterial arthritis. N Engl J Med 1985; 312:764.
- Atkins BL, Bowler IC. The diagnosis of large joint sepsis. J Hosp Infect 1998; 40:263.
- Cruz J, Clayburne GM, Sieck MS, Schumacher HR. Coexistence of calcium pyrophosphate and monosodium urate crystals in synovial fluid. (abstract) Arthritis Rheum 2001; 44:S128.
- Gálvez J, Sáiz E, Linares LF, et al. Delayed examination of synovial fluid by ordinary and polarised light microscopy to detect and identify crystals. Ann Rheum Dis 2002; 61:444.
- Lumbreras B, Pascual E, Frasquet J, et al. Analysis for crystals in synovial fluid: training of the analysts results in high consistency. Ann Rheum Dis 2005; 64:612.
- Swan A, Amer H, Dieppe P. The value of synovial fluid assays in the diagnosis of joint disease: a literature survey. Ann Rheum Dis 2002; 61:493.
- Ivorra J, Rosas J, Pascual E. Most calcium pyrophosphate crystals appear as non-birefringent. Ann Rheum Dis 1999; 58:582.
- Shmerling RH. Synovial fluid analysis. A critical reappraisal. Rheum Dis Clin North Am 1994; 20:503.
- Molloy ES, McCarthy GM. Hydroxyapatite deposition disease of the joint. Curr Rheumatol Rep 2003; 5:215.
- McGillicuddy DC, Shah KH, Friedberg RP, et al. How sensitive is the synovial fluid white blood cell count in diagnosing septic arthritis? Am J Emerg Med 2007; 25:749.
- Margaretten ME, Kohlwes J, Moore D, Bent S. Does this adult patient have septic arthritis? JAMA 2007; 297:1478.
- Shmerling RH, Delbanco TL, Tosteson AN, Trentham DE. Synovial fluid tests. What should be ordered? JAMA 1990; 264:1009.
- Kay J, Eichenfield AH, Athreya BH, et al. Synovial fluid eosinophilia in Lyme disease. Arthritis Rheum 1988; 31:1384.
- Dougados M. Synovial fluid cell analysis. Baillieres Clin Rheumatol 1996; 10:519.
- Baer PA, Tenenbaum J, Fam AG, Little H. Coexistent septic and crystal arthritis. Report of four cases and literature review. J Rheumatol 1986; 13:604.
- von Essen R, Hölttä A. Improved method of isolating bacteria from joint fluids by the use of blood culture bottles. Ann Rheum Dis 1986; 45:454.
- CATEGORIES OF JOINT EFFUSIONS
- SPECIMEN COLLECTION AND HANDLING
- Microscopic examination
- ROUTINE COMPONENTS OF SYNOVIAL FLUID ANALYSIS
- Gross appearance
- Crystal analysis
- - Monosodium urate crystals
- - Calcium pyrophosphate dihydrate crystals
- - Other crystals
- Nucleated (white) cell count and differential
- Gram stain
- Bacterial culture
- SUMMARY AND RECOMMENDATIONS