Septic arthritis: Difference between revisions
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==Background==
==Background==
* Def: inflammation of a synovial membrane with purulent effusion into the joint capsule
*Bacterial infection of a joint space — a '''true orthopedic emergency'''
* usually affects monoarticular joints (the knee is most commonly affected in adults and the hip in children)
*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>
* Relatively rare disease however because it can quickly destroy the joint or lead to osteomyelitis, fibrous ankylosis, sepsis, or even death it is important to catch and treat promptly
*Staphylococcus aureus is the most common pathogen in adults (~50%)
* Frequency is ~20,000 cases in USA/year (may be higher in pts with immunologic disorders (RA, SLE))
*Neisseria gonorrhoeae is the most common cause in sexually active young adults
* M>F predominance, usually in patients >65 years
*Knee is the most commonly affected joint (~50%)
* Etiology is usually bacterial, divided into gonococcal or nongonococcal groups
*Mortality: 5-15% overall; higher in elderly and prosthetic joints
* staph and strep are most common nongonococcal causes
* consider different organisms in children, IV drug users, and those with prosthetic joints
==Diagnosis==
* may be difficult to diagnose in early stages
* patient typically presents with fever and a warm, red, painful, swollen joint with decreased range of motion even passively
* confirm diagnosis with work up


===Infected fluid characteristics===
==Risk Factors==
# large amount (>3.5 mL)
*Pre-existing joint disease (rheumatoid arthritis, osteoarthritis)
# turbid in appearance
*Prosthetic joint
# decreased viscosity
*Recent joint surgery or injection
# 15,000->200,000 leukocytes/cubic cm (15-200 x 10^9 per L)
*IV drug use
##Likelyhood ratios:
*Immunosuppression (diabetes, HIV, steroids)
###0-25,000 = 0.33
*Skin infection or bacteremia
###25,000-50,000 = 1.06
*Advanced age
###50,000-100,000 = 3.59
###>100,000 = infinity
# 50-100% PMNs
# Poor mucin clot
# glucose >40mg/100mL less than plasma glucose
# Positive culture


==Work-Up==
==Clinical Features==
# CBC
*Acute monoarticular joint pain, swelling, warmth, erythema
# ESR
*Pain with both active and passive range of motion (distinguishes from periarticular pathology)
#Blood Cultures
*Effusion
#Gonorrhea culture (urethral/cervical/pharyngeal/rectal)  
*Fever (present in ~60%, absence does not exclude)
# Arthrocentesis with synovial fluid analysis
*In gonococcal arthritis: migratory polyarthralgias, tenosynovitis, dermatitis (pustular skin lesions), may involve multiple joints
# Plain films (often normal but may show widening of joint space or evidence of osteomyelitis)
*Prosthetic joint infection: may have subtle presentation with chronic pain and loosening
# Ultrasound (can show joint effusion, extent of disease, and may help differentiate from other conditions)


==DDx==
==Differential Diagnosis==
# toxic synovitis
*[[Gout]] / [[Pseudogout]] (crystal arthropathy)
# abscess
*[[Reactive arthritis]]
# cellulitis
*[[Rheumatoid arthritis]] flare
# primary rheumatologic disorder (i.e. vasculitis)
*Hemarthrosis
# iatrogenic
*[[Lyme disease]] (Lyme arthritis)
# reactive arthritis (post infectious)
*Viral arthritis
*[[Osteomyelitis]] with joint extension
*Periarticular abscess or [[Bursitis|bursitis]]


==Gonococcal Arthritis==
==Evaluation==
Healthy, young sexually active adults
*'''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
**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


Women > men
==Management==
*'''Empiric IV antibiotics''' after arthrocentesis (do NOT delay if aspiration will be delayed):
Suppurative monoarthritis (may be preceded by polyarthralgias)
**Vancomycin 15-20 mg/kg IV (covers MRSA) PLUS
 
**Ceftriaxone 2 g IV (covers gram-negatives and gonococcus)
Knee, wrist, ankle
**If prosthetic joint: add Vancomycin + Cefepime or Meropenem
 
*Orthopedic consultation for:
==Arthritis-Dermatitis Syndrome==
**Joint washout/irrigation (arthroscopic or open)
===Diagnosis===
**Prosthetic joint infections require urgent surgical intervention
#Triad: dermatitis, tenosynovitis, migratory polyarthritis (hematogenous spread of bacteria and immune complexes)
*Gonococcal arthritis: Ceftriaxone 1 g IV/IM daily + treat for chlamydia
#Skin lesions: scattered small painless erythematous macules or petechiae-->pustular -->necrotic lesions
*Pain management: IV analgesics, joint immobilization, ice
#Transient painful extensor tenosynovitis (writs, hands, ankles)
#Asymmtric polyarthralgia of extremity joints
#Diagnosis Cx everything - jt, mucosal surfaces, lesions
 
===Treatment===
CTX 1gIV qd OR
 
Cefotax 1g q8
 
Empirically treat Chlamydia
 
==Nongonococcal Arthritis==
===Background===
Fulminant presentation (abrupt, swelling, toxicity and fever) unless elderly
#Hematogenous
#Contiguous
#Direct traumatic implantation
#Postop
 
===Causes===
#Bacterial
#Mycobacterial
#Spirochete (lyme, syphilis)
#Fungal
#Viral (HIV, Hep B, Rubella, etc)
#Postinfectious
 
===Diagnosis===
#Synovial fluid aspiration
#Cx - if only one test, use BCx bottles (may enhance yield)
#Grm stain - 80% positive in gram-positive infxn; less sens in gram-negative
#Cell count with dif - >50,000-150,000; PMN > 90%
 
===Treatment===
#PCN-ase resistant synthetic PCN:
##Nafcillin 1-2g
##Cefazolin 1-2g
 
AND
#3rd gen ceph
 
OR
 
Vanc^
 
^new evidence suggests significantly increased rate of MRSA septic arthritis
 
^^cell counts are as low as 20,000 in MRSA Cx + synovial fluid
 
==Treatment==
# drainage of the joint
# IV Antibiotics
# generally Oxacillin or Nafcillin with a cephalosporin (ceftriaxone, feotaxme, ceftizoxime) will cover
# add vancomycin if you suspect MRSA
# in IVDA patients use IV aminoglycoside + antipseudomonal cephalosporin
# patients with prosthetic joints are at higher risk of MRSA, MRSE, Enterobacteriaceae, and Pseudomonas
# consider gonococcal infection in young sexually active patients (treat with ceftriaxone)
# Open drainage and lavage in the OR


==Disposition==
==Disposition==
* All patients should be admitted with Ortho consult and continued on IV antibiotics  
*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==
==See Also==
*[[Gout]]
*[[Pseudogout]]
*[[Osteomyelitis]]
*[[Prosthetic joint infection]]
*[[Arthrocentesis]]
*[[Arthrocentesis]]
*[[Monoarticular Arthritis]]
*[[Septic Arthritis (Hip)]]
*[[Septic Arthritis (Peds)]]


==Source==
==References==
http://emprocedures.com/arthrocentesis/analysis.htmEmedicine
<references/>


[[Category:ID]]
[[Category:Orthopedics]]
[[Category:Ortho]]
[[Category:Infectious Disease]]

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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