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Septic arthritis

Last updated: March 18, 2021

Summarytoggle arrow icon

Septic (infectious) arthritis is a bacterial infection of the joint space. Contamination occurs either via the bloodstream, iatrogenically, or by local extension (e.g., penetrating trauma). Patients with damaged (e.g., patients with rheumatoid arthritis) or prosthetic joints have an increased risk. Patients usually present with an acutely swollen, painful joint, limited range of motion, and a fever. Suspected infectious arthritis requires prompt arthrocentesis for diagnosis. In addition to the immediate broad-spectrum antibiotic therapy, surgical drainage and debridement may be necessary to prevent cartilage destruction and sepsis.

Prosthetic joint infection [3][4]

  • Etiology
  • Clinical features
    • Usually prolonged, low-grade course
    • Minimal swelling, with or without a sinus that drains pus
    • Can present acutely (see “Clinical features” above)
  • Diagnostics
    • Conventional x-ray: loosening of the prosthesis, periosteal reactions
    • For other diagnostic tests, see “Diagnostics” below.
  • Therapy
    • Removal of the prosthesis and administration of IV antibiotics for 6–8 weeks
    • Reimplantation of the prosthesis following antibiotic treatment

In order to avoid infection, strict sterile techniques should be ensured in any procedure that involves penetration of the joint space.

Bacterial coxitis (septic arthritis of the hip) [5]

  • Description: a rare condition that requires urgent treatment to avoid destruction of the joint
  • Etiology: S. aureus and group A streptococcus account for the majority of cases
  • Clinical findings
    • Joint pain (may be referred to the groin or knee)
    • Patient's hip is often flexed and externally rotated (this decreases intraarticular pressure and alleviates pain)
    • See “Clinical features” above
  • Diagnostics: For diagnostics and therapy, see respective sections below.

Bacterial coxitis is an orthopedic emergency!

Gonococcal arthritis

In a young, sexually active adult presenting with classic symptoms of septic arthritis, gonococcal infection must be ruled out.

Lyme disease


Modalities [6][7]

Suspected septic arthritis requires aspiration of synovial fluid for analysis.

Differential diagnosis based on synovial fluid analysis findings

  • Synovial fluid analysis: comprises a group of tests that examine joint fluid (synovial fluid) to aid in definitively establishing specific types of arthritis.
Interpretation of synovial fluid analysis
Appearance WBCs/μl (PMN %) Glucose levels Culture Crystals
Normal synovial fluid
  • Transparent
  • Clear and viscous
  • < 200 (< 25%)
  • Nearly equal to blood
  • Negative
  • None

Noninflammatory arthritis

E.g., osteoarthritis

  • Transparent
  • Yellow and viscous
  • 200–2000 (< 25%)
  • Nearly equal to blood
  • Negative


E.g., rheumatoid arthritis, SLE, gout, pseudogout

  • Translucent-opaque
  • Yellow and watery
  • > 2,000 (≥ 50%)
  • Lower than blood
  • Negative


E.g., bacterial infections

  • Cloudy-opaque
  • Yellow or green with variable viscosity
  • > 50,000 (≥ 75%)
  • Early: > 10,000 (≥ 75%)
  • Much lower than blood
  • Usually positive
  • None


E.g., trauma

  • Cloudy
  • Reddish with variable viscosity
  • 200–2,000 (50%–75%)
  • Nearly equal to blood
  • Negative
  • None

Further differential diagnoses to consider

Viral arthritis

Fungal arthritis [9]

See “Overview of fungal infections” in the “General mycology.”


The differential diagnoses listed here are not exhaustive.

Initial management

Following arthrocentesis and culture, simultaneous empiric antibiotic therapy (based on gram stain) and evacuation of purulent material should be performed. [8]

Further management

Treatment of adults after culture has returned [8][12]

Treatment of children [11]

We list the most important complications. The selection is not exhaustive.

  1. Goldman L, Schafer AI. Goldman-Cecil Medicine, 25th Edition. Elsevier ; 2016
  2. Chun KC, Kim KM, Chun CH. Infection following total knee arthroplasty.. Knee surgery & related research. 2013; 25 (3): p.93-9. doi: 10.5792/ksrr.2013.25.3.93 . | Open in Read by QxMD
  3. Margaretten ME, Kohlwes J, Moore D, Bent S. Does this adult patient have septic arthritis?. JAMA. 2007; 297 (13): p.1478-1488.
  4. Betts RF, Penn RL, Chapman SW. Reese and Betts' a Practical Approach to Infectious Diseases. Lippincott Williams & Wilkins ; 2003
  5. Horowitz DL, Katzap E, Horowitz S, Barilla-LaBarca ML. Approach to Septic Arthritis. Am Fam Physician. 2011; 84 (6): p.653-660.
  6. Mathews CJ, Kingsley G, Field M et al. Management of septic arthritis: a systematic review. Ann Rheum Dis. 2007; 66 (4): p.440-445. doi: 10.1136/ard.2006.058909 . | Open in Read by QxMD
  7. Liu C, Bayer A, Cosgrove SE et al. Clinical Practice Guidelines by the Infectious Diseases Society of America for the Treatment of Methicillin-Resistant Staphylococcus Aureus Infections in Adults and Children. Clin Infect Dis. 2011; 52 (3): p.e18-55. doi: 10.1093/cid/ciq146 . | Open in Read by QxMD
  8. Septic Arthritis/Infection Native Joints. Updated: January 1, 2018. Accessed: January 20, 2019.
  9. Mabille C, El Samad Y, Joseph C, et al. Medical versus surgical treatment in native hip and knee septic arthritis. Med Mal Infect. 2020 . doi: 10.1016/j.medmal.2020.04.019 . | Open in Read by QxMD
  10. Bennett JE, Dolin R, Blaser MJ. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Elsevier Saunders ; 2015
  11. Tande AJ, Patel R. Prosthetic joint infection. Clin Microbiol Rev. 2014; 27 (2): p.302-345. doi: 10.1128/CMR.00111-13 . | Open in Read by QxMD
  12. Betts RF, Chapman SW, Penn RL. Reese and Betts' A Practical Approach to Infectious Diseases. Lippincott Williams & Wilkins ; 2002
  13. Berry DJ, Lieberman J, Keeney J. Surgery of the Hip. Elsevier Saunders ; 2013