Acute monoarthritis

Classification of arthritis by numberof joints involved
1: Monoarthritis 2-3: Oligoarthritis >3: Polyarthritis Causes of migratory arthritis
  • Trauma
  • Infection
  • Crystal arthropathy
  • Acute osteoarthritis
  • Reactive arthritis
  • Lyme disease
  • Avascular necrosis
  • Tumour
  • Rheumatoid arthritis
  • SLE
  • Viral arthritis
  • Chronic osteoarthritis
  • Rheumatic fever
  • Infective endocarditis
  • Henoch Schonlein purpura
  • Serum sickness (esp. cefaclor sensitivity )
  • Viral arthritis
  • Septicaemia: staph, strep, mening/gonococcal
  • Pulmonary infection: mycoplasma, histoplasmosis
  • Lyme disease

Assessing monoarthritis


  • Trauma?
  • Night pain, morning stiffness, systemic symptoms, recent non-articular infections
  • Sexual history, previous episodes (back pain), rash


  • Joint line tenderness, movements, erythema, local increases in temperature, swelling, loss of joint function, muscle wasting
  • General examination for peripheral stigmata ( eg occular inflammation, mouth ulcers, psoriasis, erythema nodosum, vasculitic lesions )


  • FBC
  • ESR, urate
  • Renal and liver function ± blood culture ± serum for strep titres
  • Urine culture
  • Cultures for STDs if indicated
  • Arthrocentesis- sterile technique, samples:
    • Direct microscopy
    • C & S samples
    • Samples into blood culture media
    • Fluid in FBC bottle for WCC etc
  • x-rays normal for >2 weeks even in septic

  Normal Noninflammatory Inflammatory Septic
Clarity Transparent Transparent Cloudy Cloudy
Colour Clear Yellow Yellow Yellow
WBC <200 200-2000 200-50000 >50000
PMNs <25% <25% >50% >50%
Culture Neg Neg Neg >50% +ve
Crystals None None Possibly None
Associated   OA, trauma, ARF Gout, pseudogout, spondyloarthropathies, RA, Lyme disease Gonococcal and non-gonococcal sepsis, SLE

Gonococcal septic arthritis

  • Young adults, F > M
  • From disseminated gonococcal infection
  • Complicates 1-3% of all cases of gonnorhoea.
  • May haave preceding migratory tendonitis or arthritis.
  • ± vesiculopustular lesions, (esp. hands)
  • ± multiple painless macules on limbs and trunk
  • Generally large joints.
  • Synovial fluid cultures are often negative
    • …. the gonococcus has to be grown from elsewhere
  • Note that reactive arthritis secondary to gonococcal infection is a separate entity.
  • Treatment: Ceftriaxone or cefotaxime

Non-gonococcal septic arthritis

  • Extreme of age and immunocompromised.
  • NB prosthetic joints and rheumatoid arthritis
  • Irreversible loss of joint function in 25%
  • Fatality rate is 10% (higher in rheumatoid)
  • Large joints (textbook is knee)
  • 10% SIJ, 10% are polyarticular.
  • Haematogenous or local spread
  • May not be systemically unwell
  • Staph > streptococcus
  • G-ve and mycobacterium in immonocompromised
  • Joint aspirate more sensitive than blood cultures
  • Treatment: beta-lactam and an aminoglycoside / 2nd generation quinolone until sensitivities known

Crystal arthropathies

More on the Gout / Pseudogout page

Lyme disease

  • Delayed from the time of spirochete infection.
  • A history of tick bite, followed the rash of erythema chronicum migrans, is diagnostic.
  • Arthritis typically an asymmetric mono- or oligoarthritis, affecting large joints.
  • May be migratory

Reiters syndrome

More on the Reiter's syndroms page

Other causes of monoarthritis incude:

  • Ankylosing spondylitis
  • Tumours ( local, metastatic, haematological, or as part of a paraneoplastic syndrome)
  • Rheumatoid arthritis
  • Osteoarthritis

Reactive arthritis

  • A sterile joint inflammation that may be related to a distant infection

Infectious agents include:

  • Salmonella
  • Shigella
  • Yersinia
  • Campylobacter
  • Chlamydia
  • Streptococcus
  • Viruses such as
    • rubella, Hep B, parvovirus,
    • EBV, CMV, HIV, mumps


Symptoms Diagnosis Action
Clear cut septic joint or Septic infected joint   Urgent orthopaedic referral
Skin rash Swollen joint Unwell Sepsis Consider :psoriasis, viral, connective tissue disorders Referral rheumatology SpR or on-take medical SpR
Very painful joint swelling 
No trauma
Gout / Pseudgout Uric acid level
Diagnostic joint aspirate
NSAIDs (See gout)
GP follow up in next week
Admit if intractable pain or Dx unclear 
Non-specific urethritis
Diarrhoea & Joint pain
Reactive arthritis OPD follow up Local "Early arthritis" referral policy
Early morning stiffness, joint pains
Swelling of hand, wrist, MTP or MCPs
? Early rheumatoid arthritis OPD follow up Local "Early arthritis" referral policy
Patient well Background of OA Mild trauma Age > 50 Probable osteo-arthritis NSAIDs GP follow up


Content by Dr Íomhar O' Sullivan 29/12/2010. Last updated Dr ÍOS 19/06/21.