Septic arthritis: Difference between revisions

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== Background ==
==Background==
*Most important diagnostic consideration in acute joint pain (can destroy joint in days)
*Bacterial infection of a joint space — a '''true orthopedic emergency'''
*Knee most commonly involved in adults; hip most common in peds
*Rapid cartilage destruction occurs within hours if untreated<ref name="mathews">Mathews CJ, et al. Bacterial septic arthritis in adults. ''Lancet''. 2010;375(9717):846-855. PMID 20206778.</ref>
*Most often seen in pts &gt;65yr
*Staphylococcus aureus is the most common pathogen in adults (~50%)
*Gonococcal arthritis is commonest cause in adolescents and young adults
*Neisseria gonorrhoeae is the most common cause in sexually active young adults
*Knee is the most commonly affected joint (~50%)
*Mortality: 5-15% overall; higher in elderly and prosthetic joints


== Clinical Features ==
==Risk Factors==
*Fever
*Pre-existing joint disease (rheumatoid arthritis, osteoarthritis)
*Warm, red, painful, swollen joint  
*Prosthetic joint
*Decreased range of motion to active and passive movement
*Recent joint surgery or injection
*Gonococcal arthritis may have prodromal phase:
*IV drug use
**Migratory arthritis and tenosynovitis predominate before pain and swelling occurs
*Immunosuppression (diabetes, HIV, steroids)
*Skin infection or bacteremia
*Advanced age


== Diagnosis ==
==Clinical Features==
*Acute monoarticular joint pain, swelling, warmth, erythema
*Pain with both active and passive range of motion (distinguishes from periarticular pathology)
*Effusion
*Fever (present in ~60%, absence does not exclude)
*In gonococcal arthritis: migratory polyarthralgias, tenosynovitis, dermatitis (pustular skin lesions), may involve multiple joints
*Prosthetic joint infection: may have subtle presentation with chronic pain and loosening


*Arthrocentesis for synoval fluid
==Differential Diagnosis==
*[[Gout]] / [[Pseudogout]] (crystal arthropathy)
*[[Reactive arthritis]]
*[[Rheumatoid arthritis]] flare
*Hemarthrosis
*[[Lyme disease]] (Lyme arthritis)
*Viral arthritis
*[[Osteomyelitis]] with joint extension
*Periarticular abscess or [[Bursitis|bursitis]]


{| width="400" border="1" cellpadding="1" cellspacing="1"
==Evaluation==
|-
*'''Arthrocentesis''' — '''must be performed''' in any suspected septic joint<ref name="long">Long B, et al. Evaluation and Management of Septic Arthritis and its Mimics in the Emergency Department. ''West J Emerg Med''. 2019;20(2):331-341. PMID 30881554.</ref>
|
**Send for: cell count with differential, Gram stain, culture, crystal analysis
| Normal
**WBC >50,000/mm³ with >90% PMNs strongly suggests infection
| Noninflammatory
**WBC >100,000/mm³ is virtually diagnostic
| Inflammatory
**Lower counts do not exclude — partially treated or early infection may have lower counts
| Septic
**Gram stain positive in ~50% of non-gonococcal cases
|-
*Labs: CBC, ESR, CRP, blood cultures (positive in ~50%), lactate
| Clarity
*If gonococcal suspected: GC/CT NAAT (urine, cervix/urethra, pharynx, rectum)
| Transparent
*Imaging:
| Transparent
**X-ray: evaluate for effusion, osteomyelitis, fracture
| Cloudy
**Ultrasound: guide arthrocentesis, confirm effusion
| Cloudy
**MRI if concerned for adjacent osteomyelitis
|-
| Color
| Clear
| Yellow
| Yellow
| Yellow
|-
| WBC
| &lt;200
| &lt;200-2000
| 200-50,000
| &gt;25,000
|-
| PMN
| &lt;25%
| &lt;25%
| &gt;50%
| &gt;90%
|-
| Culture
| Neg
| Neg
| Neg
| &gt;50% positive
|-
| Crystals
| None
| None
| Multiple or none
| None
|}


== DDx ==
==Management==
#Toxic synovitis
*'''Empiric IV antibiotics''' after arthrocentesis (do NOT delay if aspiration will be delayed):
#Abscess
**Vancomycin 15-20 mg/kg IV (covers MRSA) PLUS
#Cellulitis
**Ceftriaxone 2 g IV (covers gram-negatives and gonococcus)
#Primary rheumatologic disorder (i.e. vasculitis)  
**If prosthetic joint: add Vancomycin + Cefepime or Meropenem
#Iatrogenic
*Orthopedic consultation for:
#Reactive arthritis (post-infectious)
**Joint washout/irrigation (arthroscopic or open)
**Prosthetic joint infections require urgent surgical intervention
*Gonococcal arthritis: Ceftriaxone 1 g IV/IM daily + treat for chlamydia
*Pain management: IV analgesics, joint immobilization, ice


== Work-Up ==
==Disposition==
#Arthrocentesis with synovial fluid analysis
*Admit all confirmed or suspected septic arthritis
##Synovial fluid culture only
*Orthopedic surgery consultation for joint washout
#CBC
*Gonococcal arthritis: may be managed with close outpatient follow-up after initial IV antibiotics in select cases
#ESR
##Sn 96% (with 30mm/h cut-off)
#Blood Culture
#Gonorrhea culture (urethral/cervical/pharyngeal/rectal)
#Plain films (often normal but may show widening of joint space or evidence of osteomyelitis)
#Ultrasound (can show joint effusion, extent of disease, and may help differentiate from other conditions)


== Treatment ==
==See Also==
#Joint drainage
*[[Gout]]
#Abx
*[[Pseudogout]]
##Gram stain can be used to guide treatment
*[[Osteomyelitis]]
###Gram+: vancomycin IV
*[[Prosthetic joint infection]]
###Gram- OR gonococcus suspected: Ceftriaxone IV
*[[Arthrocentesis]]
#Consult ortho for joint irrigation in OR if joint aspirate is indicative of infection


== Disposition ==
==References==
*Admit all to ortho
<references/>


== See Also ==
[[Category:Orthopedics]]
*[[Arthrocentesis]]
[[Category:Infectious Disease]]
*[[Monoarticular Arthritis]]
*[[Septic Arthritis (Hip)]]
*[[Septic Arthritis (Peds)]]
 
== Source ==
*Tintinalli
 
[[Category:ID]] [[Category:Ortho]]

Latest revision as of 09:31, 22 March 2026

Background

  • Bacterial infection of a joint space — a true orthopedic emergency
  • Rapid cartilage destruction occurs within hours if untreated[1]
  • Staphylococcus aureus is the most common pathogen in adults (~50%)
  • Neisseria gonorrhoeae is the most common cause in sexually active young adults
  • Knee is the most commonly affected joint (~50%)
  • Mortality: 5-15% overall; higher in elderly and prosthetic joints

Risk Factors

  • Pre-existing joint disease (rheumatoid arthritis, osteoarthritis)
  • Prosthetic joint
  • Recent joint surgery or injection
  • IV drug use
  • Immunosuppression (diabetes, HIV, steroids)
  • Skin infection or bacteremia
  • Advanced age

Clinical Features

  • Acute monoarticular joint pain, swelling, warmth, erythema
  • Pain with both active and passive range of motion (distinguishes from periarticular pathology)
  • Effusion
  • Fever (present in ~60%, absence does not exclude)
  • In gonococcal arthritis: migratory polyarthralgias, tenosynovitis, dermatitis (pustular skin lesions), may involve multiple joints
  • Prosthetic joint infection: may have subtle presentation with chronic pain and loosening

Differential Diagnosis

Evaluation

  • Arthrocentesis — must be performed in any suspected septic joint[2]
    • Send for: cell count with differential, Gram stain, culture, crystal analysis
    • WBC >50,000/mm³ with >90% PMNs strongly suggests infection
    • WBC >100,000/mm³ is virtually diagnostic
    • Lower counts do not exclude — partially treated or early infection may have lower counts
    • Gram stain positive in ~50% of non-gonococcal cases
  • Labs: CBC, ESR, CRP, blood cultures (positive in ~50%), lactate
  • If gonococcal suspected: GC/CT NAAT (urine, cervix/urethra, pharynx, rectum)
  • Imaging:
    • X-ray: evaluate for effusion, osteomyelitis, fracture
    • Ultrasound: guide arthrocentesis, confirm effusion
    • MRI if concerned for adjacent osteomyelitis

Management

  • Empiric IV antibiotics after arthrocentesis (do NOT delay if aspiration will be delayed):
    • Vancomycin 15-20 mg/kg IV (covers MRSA) PLUS
    • Ceftriaxone 2 g IV (covers gram-negatives and gonococcus)
    • If prosthetic joint: add Vancomycin + Cefepime or Meropenem
  • Orthopedic consultation for:
    • Joint washout/irrigation (arthroscopic or open)
    • Prosthetic joint infections require urgent surgical intervention
  • Gonococcal arthritis: Ceftriaxone 1 g IV/IM daily + treat for chlamydia
  • Pain management: IV analgesics, joint immobilization, ice

Disposition

  • Admit all confirmed or suspected septic arthritis
  • Orthopedic surgery consultation for joint washout
  • Gonococcal arthritis: may be managed with close outpatient follow-up after initial IV antibiotics in select cases

See Also

References

  1. ↑ Mathews CJ, et al. Bacterial septic arthritis in adults. Lancet. 2010;375(9717):846-855. PMID 20206778.
  2. ↑ Long B, et al. Evaluation and Management of Septic Arthritis and its Mimics in the Emergency Department. West J Emerg Med. 2019;20(2):331-341. PMID 30881554.
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