Keywords: Synovial effusion


Appropriate Tests


Careful clinical assessment: diagnostic imaging and pathology tests contribute to diagnosis, assessment of severity and complications, monitoring of disease activity and drug therapy.

Full blood count. C-Reactive protein. Erythrocyte sedimentation rate. Joint aspiration may be indicated; Synovial fluid examination with tests as appropriate to the clinical context. Synovial biopsy, if indicated.

Polyarticular arthritis  

Rheumatoid factor, Antinuclear Ab and Extractable nuclear antigen Ab, Cyclic citrullinated peptide Ab.

Rheumatoid arthritis


Virus-associated arthritis

Rubella Ab, Arbovirus Ab (Ross River virus, Barmah Forest virus, Zika virus, Chikungunya virus), Cytomegalovirus Ab and Parvovirus B19 Ab, Hepatitis B virus testing serology, HIV serology.

Connective tissue disease, especially


  • SLE


Seronegative arthritis, especially


  • Ankylosing spondylitis

Rheumatoid factor-negative spondylo-arthropathies associated with HLA-B27.

  • Reactive arthritis


  • Inflammatory bowel disease

In the acute phase, microbiological studies may be useful to identify the precipitating infection: Faeces MCS and antigen (Salmonella, Shigella, Campylobacter, Yersinia sp); Genital swab (urethral or cervical) or urine for Chlamydia trachomatis nucleic acid detection. Specific PCR testing.

  • Psoriatic arthritis


Lyme disease

Borrelia burgdorferi Ab.

Rheumatic fever

Throat swab for detection of Group A beta haemolytic streptococcus, Antistreptolysin O titre (ASOT) on serum.



Paraprotein-associated arthritis

See Paraproteinaemia.

Mono- or oligo-articular arthritis


Degenerative joint disease (osteoarthritis) and gout

Joint aspiration is frequently indicated; Synovial fluid examination, including microscopy for crystals and bacterial culture, other tests as appropriate.

Chondrocalcinosis (pseudogout)


Seronegative arthritis, especially


  • Ankylosing spondylitis


  • Inflammatory bowel disease


  • Psoriatic arthritis


  • Reiter's syndrome

Look for concomitant or recently treated gonococcal or chlamydial infection of mucous membranes.


HIV serology (HIV antibodies)

Rheumatoid arthritis


Septic arthritis (joint suspected) 

Blood culture, Urea, Electrolytes, Glucose, consider Liver function tests and Urate, C-Reactive protein, Full blood count, Ward test urine, MCS on joint aspirate.

See Guideline on Pathology testing in the Emergency department: Appendix 2.

  • Pyogenic arthritis

Synovial fluid examination (cell count and differential and culture) must be performed. Blood culture should also be performed.

Chronic haemophilic arthropathy



See Haemophilia (A and B).

  • Trauma


  • Haemophilia

Joint aspiration is rarely necessary and must not be performed without prior consultation with a Haemophilia Treatment Centre.



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