Septic Arthritis (quick review)

24 Nov

Risk Factors:

  • Age >80 years
  • Diabetes mellitus
  • Presence of prosthetic joint
  • Skin infection
  • Rheumatoid arthritis
  • Recent joint surgery
  • Intravenous drug abuse, alcoholism
  • Corticosteroid injection


Bacteremia is more likely to localize in a joint with preexisting arthritis, particularly if associated with synovitis.  Patients with RA may have additional predisposing factors, such as prior intraarticular steroid injections, maintenance immunosuppressive medications, and anti-tumor necrosis factor (TNF) therapy [1]. 


Mechanism:  Hematogenous spread to the joint.   Bacterial arthritis can also arise as a result of a bite or other trauma, direct inoculation of bacteria during joint surgery. 

Because synovial tissue has no limiting basement plate, bacterial organisms can quickly gain access to the synovial fluid, creating acute-onset joint inflammation with purulence. Following onset of infection, there is marked hyperplasia of the lining cells in the synovial membrane within seven days (1).


Differential Diagnosis

Reiter’s syndrome, pseudogout, GC arthritis, Lyme disease, RA, osteoarthritis, reactive arthritis


Clinical Manifestations:

A majority of patients with bacterial arthritis are febrile.  Older adult patients with septic arthritis are less likely to present with fever.  


Joint Aspiration:   Since this condition represents a closed abscess collection, the joint space should be drained. After initiation of treatment, serial synovial fluid analyses should reveal decrease inflammatory burden.


Synovial Fluid Profile

Greater > 2000 leukocytes/ml (5):

  • Traumatic Arthritis – < 5,000  (w/ RBCs) (5)
  • Reactive Arthritis – Recent genitourinary or gastrointestinal signs or symptoms, conjunctivitis, or skin or mucus membrane lesions (1).
  • Rheumatoid Arthritis – 10,000- 15,000 and 50 % polymorphs. Sterile incr protein, & decreased viscosity & decreased complement (5).
  • Toxic Synovitis – 15,000 and less than < 25 % polymorphs (5)

Greater > 50,000 leukocytes/ml (5):

  • Gout/Psuedogout – Synovial fluid analysis to r/in crystals (5).
  • Septic Arthritis – 80,000-200,000 and > 75% polymorphs (5).


ManagementOrthopaedics C/S and antimicrobial therapy

Antibiotic Therapy based on Synovial Fluid Analysis

If (+) GPC, treat w/ Vancomycin 30mg/kg q daily.

If (+) GNR, treat w/ Ceftriaxone 2g IV q daily. Duration of therapy:  Recommend IV x 14 days and transition to PO.

Complications – Cartilage degradation and inhibition of cartilage synthesis. Pressure necrosis from large synovial effusions may result in further cartilage and bone loss (1).


PrognosisInflammation and joint destruction may continue even in the setting of a sterile joint, despite effective antimicrobial therapy [1].


Submitted by Christina Brown, M.D.



  2. Mor A, Mitnick HJ, Greene JB, et al. Relapsing oligoarticular septic arthritis during etanercept treatment of rheumatoid arthritis. J Clin Rheumatol 2006; 12:87.
  1. Margaretten ME, Kohlwes J, Moore D, Bent S. Does this adult patient have septic arthritis? JAMA 2007; 297:1478.
  2. Goldenberg DL. Septic arthritis. Lancet 1998; 351:197.
  2. picture 1, picture 2

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