Acute Monoarthritis: A Rheumatologic Emergency

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Acute Monoarthritis A Rheumatologic Emergency

• Kyle C. Harner, MD

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References

• Baker and Schumacher, Acute Monoarthritis. NEJM
  1993 Sept 30329(14) 1013-20.
• Freed et al, Acute Monoarticular arthritis. A
  diagnostic approach. JAMA 1980 June 13
  243(22) 2314-6.
• Towheed and Hochberg, Acute Monoarthritis a
  practical approach to assessment and
  treatment. Am Fam Physician 1996 Nov 15
  54(7) 2239-43.

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Differential Diagnosis

• Infectious arthritis ()
• Crystal-induced arthritis ()
• Trauma ()
• Osteoarthritis
• Osteonecrosis
• Foreign-body reaction

• Tumor
• Presentation of systematic disease Three most
  common causes

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Infectious Arthritis

• Most serious cause of monoarthritis, can destroy
  cartilage in one to two days
• Non-gonococcal are most serious - most
  common in knees and hips - sternoclavicular
  joints in IV drug users - most febrile but do
  not appear especially ill - 90 monoarticular,
  hematogenous spread - 80 Gram() anaerobes
  60 S. Aureus (most PCN, some meth
  resistant) 15 Non-group A, beta-hemolytic
  strep 3 Strep pneumo - 18
  Gram(-) - Anearobes on rise in IV drug
  users/immunocompromised

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Infectious Arthritis (cont.)

• Gonococcal - Women men - Often
  proceeded by migratory tendonitis/arthritis -
  Much less destructive as extremely sensitive to
  ABX - Cephalosporins standard of care now, due
  to PCN resistant strains - Synovial fluid
  culture only positive in 25 of cases
• Tuberculous - Most often chronic, but
  reported acute cases - Pulmonary TB on seen in
  50 of patients w/ joint findings - PPD usually
  positive
• Fungal
• Viral (such as herpes simplex and HIV)
• Lyme - characteristic acute oligoarthritis

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Crystal-induced Arthritis

• Gout (monosodium urate crystals) most common -
  First MTP, ankle, midfoot, knee (can be any joint
  though) - Most initial attacks affect a single
  joint - Fever (more common with polyarticular)
  can raise suspicion for infection -
  Presence of crystal does not exclude
  infection - May see desquamation of overlying
  skin - Thiazide diuretics can put at risk -
  Needle shaped, negatively birefringent crystals
• Calcium pyrophosphate dihydrate/pseudogout -
  Clinically not able to distinguish from gout -
  Most common in knee and wrists - Evolves over
  several days (less acute than gout) - Rhomboid
  shaped, positively birefringent crystals
• Other crystals apatite, calcium oxalate, liquid
  lipid

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Other causes

• Osteoarthritis - acutely worse and swollen in
  single joint (overuse)
• Osteonecrosis - common in elderly, sudden onset
  of pain or swelling in single joint with or
  without effusion
• Hemarthrosis (bleeding into joint) - most common
  in folks with acquired or congenital clotting
  problems (such as hemophilia)
• Penetrating injuries (wood fragments, thorns) can
  lead to foreign body reaction
• Prosthetic joint - infection most likely due to
  seeding from skin source, crystal disease is
  rare. Loosening is most common cause of pain
• RA, SLE, IBD, Psoriatic arthritis, Behcets,
  Reiters
• Idiopathic (relatively good prognosis for
  undiagnosed cases)

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Approach to the Patient

• Previous history - crystal induced versus
  non-infectious
• Fever, tick bites, sexual risk factors, IV drug
  use, travel, trauma
• Sx rash, diarrhea, urethritis, uveitis
• PE joint (rubor/dolor/calor/tumor), ulcers
  (Behcets, Reiters, SLE), psoriasis, erythema
  nodosum (SLE, sarcoidosis, IBD), splinter
  hemorrhages (bacterial endocarditis)
• Radiographs - not often helpful in establishing
  diagnosis
• Culture and gram stain of joint and any other
  lesions
• HIV and lyme titer if indicated
• RF, ANA, and acute uric acid not often helpful
• Arthrocentesis (only need 1 to 2 cc) in almost
  all patients, send fluid for crystals, gram
  stain/culture, cell count
• Rarely need to proceed to arthroscopy/synovial
  biopsy

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Synovial fluid cell count interpretation

• Leukocyte count 2000 2000-20,00
  0 20,000-50,000 50,000 100,000
• 90 PMNs despite count, concern for gout/septic
  joint

• Interpretation Normal Non-inflammatory Inflammat
  ory Mild inflam (SLE) Mod. inflam
  (RA) Severe(gout,septic) Septic, until
  proven otherwise

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Treatment

• Treat for gram() infection including
  methicillin-resistant staph. and strep.
• Treat for gram(-) as well in immunocompromised
  patients and patients with gram(-) source
• IV Ceftriaxone for gonococcal arthritis (most
  areas)
• Daily closed drainage until effusion is gone
• Consider open drainage if response to IV
  antibiotics is slow or if joint can not be
  aspirated (? arthroscopic drainage in some
  centers)
• Culture negative, ? stop antibiotics
• Joint rest, ice, PT