Arthritis - Approach
- First step to to determine extent of involvement: mono vs oligo vs polyarthritis
- Monoarthritis:
- Differential diagnosis
- Trauma: hemarthrosis, fracture, ligamentous injury
- Infection: staphylococcus, streptococcus, neisseria, GNRs, TB, fungal, Lyme
- Crystal: gout, pseudogout
- Rheumatologic: seronegative spondylarthropathy, sarcoid, RA, OA
- History: assess timing, antecedent trauma, systemic complaints
- Exam: presence of synovitis (warmth, swelling, effusion), indicates that inflammatory process is present
- Septic and crystal arthritis have nearly identical clinical features, and can occur concomitantly
- Fever, leukocytosis, ESR, and CRP are non-specific (see attached JAMA article)
- Management: Given the difficulty in differentiating, aspiration should be performed in all joints with signs of inflammation
- Aspiration: send cell count, GS, culture, crystals
- Cell count:
- >2K WBC/mm3 indicates inflammatory process
- >50K WBC/mm3 suggests infection (+LR 7.7), with higher levels more strongly suggestive
- However, this is not a clean dichotomy, and overlap exists
- >90% PMNs also suggests infection (+LR 3.4)
- Cell count:
- Treatment:
- Septic arthritis: joint should be drained urgently, then IV abx x 2 weeks, followed by PO
- Pseudogout: intraarticular steroids and NSAIDs
- Aspiration: send cell count, GS, culture, crystals
(Christopher Woo MD, 11/1/10)