infectious%20arthritis
INFECTIOUS ARTHRITIS
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. 

Evaluation

  • Monitor patient for improvement of clinical signs & symptoms
  • Levels of ESR & CRP may be used to evaluate response to treatment
  • Specialist referral should be considered in patients w/ features of sepsis for possible drainage & parenteral antibiotic therapy
  • Continue empiric treatment if patient is improving & cultures are negative
  • Serial analysis of the synovial fluid should show a decreasing WBC count & should revert to the sterile state w/ treatment
  • If a patient does not improve w/ appropriate treatment, consider:
    • Revision of antibiotic therapy
    • Open drainage of joint, biopsy & repeat culture, washout or debridement may be required
    • Repeating tests to uncover a possible non-infectious cause of arthritis
    • Consider specialist referral
  • Outpatient parenteral antibiotic therapy may be considered in patients in whom it is not feasible to complete treatment w/ oral antibiotics
    • A functioning outpatient parenteral antimicrobial therapy (OPAT) program should have a complete & qualified health care team, efficient means of communication, guidelines for follow-up, testing & other interventions, written policies & procedures & outcomes monitoring
    • A candidate for inclusion in an OPAT program should be willing to participate in the program & should have a home environment that is sufficient to support care

History

  • Family history of gout
  • Sexual history including history of N gonorrhoeae infection
  • Travel & occupational history
  • Diet & alcohol consumption

Physical Examination

  • Patients most often present w/ a red, warm, swollen & very tender joint
    • Affected joint may also present w/ effusion & severe restriction of movement
  • Exam should focus on the involved & contralateral joint & surrounding area including the skin & soft tissue
    • A general exam should be performed to search for other joint involvement, look for systemic manifestations of disease & seek extra-articular sources of infection
    • Gonococcal infections may manifest w/ fever, multiple painless macules & papules on the arms, legs or trunk, & tenosynovitis
    • Patients w/ rheumatoid arthritis may present exacerbation of inflammation in one or more joints
  • In children w/ infectious arthritis of the hip, the hip may be kept flexed & externally rotated, w/ severe pain on motion
  • Few physical signs may be found in patients w/ infectious arthritis of the spine, sacroiliac joints & hips
  • The absence of fever does not rule out infectious arthritis

Laboratory Tests

Synovial fluid exam 

  • Synovial fluid aspiration is the most important test for diagnosing infectious arthritis & should be done for all patients suspected of having infectious arthritis
  • Gram stain, culture, white blood cell (WBC) count w/ differential should be done
    • Gram stain is positive in only 60-80% of cases; a negative Gram stain &/or culture does not exclude the diagnosis of infectious arthritis
    • A WBC count of >50,000 cells/mm3 w/ neutrophil predominance is highly suggestive of bacterial arthritis
    • Synovial fluid glucose is usually decreased while protein & lactate dehydrogenase are usually increased in both inflammatory & infectious causes of arthritis
  • Routine polymerase chain reaction (PCR) is not recommended; may be useful in prosthetic joint infection to differentiate between septic & aseptic loosening & in culture-negative patients w/ similar presentation as reactive arthritis
  • Polarizing microscopy to evaluate crystals should be performed
  • Synovial biopsy is the most sensitive (95%) way to confirm a diagnosis of mycobacterial infectious arthritis

Blood culture

  • Should be obtained in all patients suspected of having infectious arthritis
  • Positive in 50% of cases

Complete blood count (CBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)

  • Used to determine presence of infection or inflammation; ESR & CRP are useful for monitoring treatment response
  • Leukocytosis is usually present (leukocyte count of 50,000-150,000 cells/mm3)
  • ESR is usually >20 mm/hour
  • CRP is usually raised; a normal CRP is a good negative predictor for infectious arthritis
  • Normal levels of ESR, CRP &/or WBC do not rule out infectious arthritis

Other laboratory tests

  • Blood urea nitrogen (BUN), creatinine & liver function tests should be taken to detect end-organ damage, a poor prognostic factor in infectious arthritis
  • Appropriate specimens from other sites (eg cervix, urethra & throat) should be taken in patients in whom genitourinary, respiratory or other infections are being considered

Imaging

  • Plain x-rays of affected joints are not very helpful in diagnosing infectious arthritis but may act as a baseline to help exclude osteomyelitis or other abnormalities of the bone
    • X-rays done during early infection are usually normal but may show soft tissue swelling, displacement of the fat pad, or joint space widening secondary to localized edema
  • Magnetic resonance imaging (MRI) is a sensitive test for distinguishing infectious arthritis from osteomyelitis & demonstrates adjacent soft tissue edema & abscesses
  • Computed tomography (CT) scan is helpful in detecting effusions & inflammation in joints that are difficult to examine because of complex anatomy (eg hip & shoulder)
  • Ultrasonography may detect fluid in suspected infectious arthritis of the hip & may be used to perform an imaging-guided joint aspiration
Digital Edition
Asia's trusted medical magazine for healthcare professionals. Get your MIMS Infectious Diseases - Malaysia digital copy today!
DOWNLOAD
Editor's Recommendations
Most Read Articles
13 Oct 2017
Use of systemic antibiotics, in conjunction with performance of incision and drainage, in the management of paediatric acute skin and soft tissue infection (SSTI) appears to reduce Staphylococcus aureus colonization and the likelihood of infection recurrence, a prospective study has found.
12 Oct 2017
Retreatment with ledipasvir and sofosbuvir with add-on ribavirin appears to be effective and well tolerated in genotype 1 hepatitis C virus (HCV)-infected patients who have failed to respond to daclatasvir/asunaprevir combination therapy, according to a study.
5 days ago
Excessive intake of the mineral manganese can be toxic to the heart, according to a new study.