Arthritis, Monoarticular

Basics

Description

  • Localized to 1 joint, not migratory
  • Infectious (septic) arthritis: Rapidly destructive process causes significant disability
    • Contiguous extension (cellulitis, osteomyelitis), hematogenous spread, direct inoculation
    • Predisposing factors:
      • Local pathology (inflammatory arthritis, trauma, prosthetic joint)
      • Immunosuppression
      • IV drug use
  • Crystal arthropathy:
    • Gout: Uric acid overproduction or underexcretion, deposited within and around joints
    • Pseudogout: Calcium pyrophosphate
  • Various arthropathies:
    • Osteoarthritis or degenerative joint disease (DJD), trauma (fractures, hemarthrosis), autoimmune disorders
    • Progressive joint destruction; mechanical dysfunction
      • Bone reactive changes (spurring)
      • Subchondral bony erosions
  • The presence of one etiology does not exclude another

Etiology

  • Infectious (septic)
    • Most common organisms nongonococcal
      • Gram-positives: Streptococcus, Staphylococcus (80%)
    • Some associations:
      • Staphylococcus aureus: Trauma, IV drug use
      • Neisseria gonorrhoeae (STI)
      • Salmonella (sickle cell) but most common causes in sickle cell Staphylococcus, Streptococcus
      • Less common: Fungal (chronic), spirochete (Lyme), viral (polyarticular), mycobacteria (TB)
  • Crystal arthropathy:
    • Gout: Uric acid overproduction, underexcretion within or around joints
    • Tophi: Crystal deposits near recurrent flare sites. Progressive enlargement, may ulcerate through skin
    • Negatively birefringent crystals
    • Pseudogout: Calcium pyrophosphate
    • Positively birefringent crystal
    • Bariatric surgery: Postoperative gout flares are a common occurrence
  • Inflammatory:
    • Rheumatoid, Psoriatic, inflammatory bowel disease, Reiter syndrome
  • Other conditions:
    • Osteoarthritis DJD, overuse, overload (obesity)
    • Trauma
    • Hemorrhagic disorders
    • Neuropathic disorders (Charcot joint)

Pediatric Considerations
  • Infectious (septic) arthritis:
    • Low incidence, high morbidity, sepsis (8%)
    • Most common: S. aureus, hip > knee, 50% coexisting osteomyelitis
    • Present like adults: Joint swollen, painful, worsened with weight bearing, movement; constitutionally ill, limp
    • Aspiration, empiric treatment, admission
  • Inflammatory:
    • A diagnosis only after septic joint excluded
    • Other considerations same as adults + juvenile idiopathic arthritis
  • Other considerations to not overlook:
    • Salter–Harris epiphyseal plate fractures
    • Congenital hip dysplasia
    • Slipped capital femoral epiphysis (SCFE)
      • Overweight adolescents
    • Legg–Calve–Perthes:
      • Avascular necrosis femoral head
      • Age 4–9
    • Bleeding disorders, hemorrhage

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