The classical presentation of infectious arthritis is acute onset of pain, warmth and swelling of a single joint.
The range of motion is usually decreased.
The knee is the most commonly affected but any joint may be involved.
Fever and chills may be present.
More than 1 joint may be involved in patients with pre-existing joint disease, other inflammatory conditions or severe sepsis, and in some patients infected with certain pathogens eg N gonorrheae, N meningitidis and Salmonella spp.
Infectious arthritis must always be a part of the differential diagnosis in a patient with an acute monoarthritis. 


S aureus

  • Most common pathogen in infectious arthritis of both native & prosthetic joints
  • Infections caused by Methicillin-resistant S aureus are usually more aggressive, w/ involvement of >1 joint

S epidermidis

  • More common in prosthetic joint infection


  • Next to S aureus, most common Gram positive aerobes causing infectious arthritis
  • Group B streptococci is a common cause of infectious arthritis in neonates while S pyogenes & S pneumoniaeare are common pathogens in children ≤ 5 years old who have infectious arthritis
  • Streptococci are important infectious arthritis pathogens in patients w/ serious infections of the genitourinary or gastrointestinal tract

Gram-negative bacilli

  • Common etiologic agents of infectious arthritis in intravenous (IV) drug users, elderly & immunocompromised persons
    • Elderly patients frequently have underlying joint diseases & concomitant diseases like diabetes mellitus (DM)  & rheumatoid arthritis
    • Disease-modifying drugs used to treat rheumatoid arthritis (eg Infliximab & Etanercept) may predispose patients to the development of infectious arthritis
  • H influenzae was formerly a common pathogen in infectious arthritis in children aged 1 month-5 years but widespread vaccination against the organism has drastically reduced the number of cases
  • P aeruginosa may be a cause of infectious arthritis in IV drugs users, premature infants & patients w/ central vascular catheters

N gonorrhoeae

  • Possible etiologic agent in young, healthy, sexually active adults w/ infectious arthritis
  • Incidence frequently related to socioeconomic status


  • More common in patients w/ DM & those w/ prosthetic joint infection

Mycobacterial species & fungi

  • Much less common cause of infectious arthritis compared to bacteria
  • Low immune system, recent travel & living in endemic areas are determinants for people susceptible to mycobacterial infections
  • Infectious arthritis caused by these organisms usually presents w/ marked joint swelling, mild signs of acute inflammation & few systemic symptoms
  • Tuberculous infectious arthritis may be more common in low-income groups while other mycobacterial species can cause infectious arthritis in human immunodeficiency virus (HIV)-infected persons
  • Candida arthritis is more common in immunocompromised persons & is associated w/ the presence of a central vascular catheter

Signs and Symptoms

  • Classical presentation: Acute onset of pain, warmth & swelling of a single joint
    • Range of motion is usually decreased
    • The knee is most commonly affected but any joint may be involved
    • >1 joint may be involved in patients w/ pre-existing joint disease, other inflammatory conditions or severe sepsis & in some patients infected w/ certain pathogens (eg N gonorrhoeae, N meningitidis & Salmonella spp)
  • Fever & chills may be present
  • Infectious arthritis must always be part of the differential diagnosis in a patient w/ an acute monoarthritis
  • Children may present w/ more subtle symptoms:
    • Anorexia, malaise, irritability
    • Limp or refusal to walk
    • Refusal to use the affected joint
    • Redness & swelling of skin & soft tissue overlying the involved joint early in the disease

Risk Factors

  • Newborns & persons >60 years old
  • Recent joint surgery, prosthetic joints, arthroscopy, osteoarthritis, rheumatoid arthritis in a specific joint, direct joint injury, open reduction of fracture & intra-articular steroid injection
  • Systemic diseases [eg rheumatoid arthritis, diabetes mellitus (DM), malignancies, use of glucocorticoids & other immunosuppressive drugs]
  • Extra-articular site of infection that may have given rise to bacteremic seeding in a joint (eg pyelonephritis, pneumonia & skin infection)
  • Alcoholism & intravenous (IV) drug abuse
  • Low socioeconomic status
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