• Clinical science

Septic arthritis (Infectious arthritis)

Summary

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.

Etiology

Clinical features

  • Acute onset
  • Classical triad of fever, joint pain, and restricted range of motion
  • Arthritis
    • Usually monoarticular
    • Most commonly affected joints: knees (followed by hip, wrists, shoulders, and ankles)
    • Joints are swollen, red, warm, and painful.

Subtypes and variants

Prosthetic joint infection [2][3]

  • Etiology
    • Early onset (< 3 months of placement): most commonly S. aureus
    • Delayed onset (3–12 months of placement); : coagulase-negative staphylococci, particularly S. epidermidis
    • Late onset (> 12 months of placement): most commonly S. aureus
  • 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) [4]

  • 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

Diagnostics

Approach

Modalities [5][6]

  • Arthrocentesis: a diagnostic and/or therapeutic procedure in which synovial fluid from a joint is aspirated using a sterile needle to determine the etiology of joint effusions and/or to relieve pressure from a joint
  • Culture and gram staining
    • Synovial fluid culture and gram stain are positive in most patients with bacterial arthritis.
    • Blood culture: at least 2 sets of blood cultures to rule out a bacteremic origin
  • Laboratory tests: CRP, ESR, and leukocyte count (nonspecific, but may be useful for monitoring response to treatment) [7]
  • Imaging: to look for signs of underlying osteomyelitis and concurrent joint disease and rule out possible differential diagnoses (see “Differential diagnosis” below)
    • Ultrasound
      • Effusion, edema of the surrounding soft tissue
      • Possible empyema
    • X-ray
      • Unremarkable early in the course of septic arthritis
      • Osteolysis usually becomes visible after 2–3 weeks.
    • MRI or scintigraphy for early detection
      • MRI provides early evidence of infectious involvement of the surrounding soft tissue
      • Scintigraphy is used for detection or exclusion of polyarticular involvement

Suspected septic arthritis requires aspiration of synovial fluid for analysis.

Differential diagnoses

Differential diagnosis based on synovial fluid analysis findings

Differential diagnosis 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

Inflammatory

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

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

Septic

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

Hemorrhagic

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 [8]

  • Etiology: Histoplasma species, Sporothrix schenckii, Blastomyces species, Coccidioides species
  • Clinical features
    • Very variable with acute and chronic courses
    • Often with symptoms of disseminated infection (e.g., pulmonary symptoms)
  • Diagnostics

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

Other

The differential diagnoses listed here are not exhaustive.

Treatment

Initial management

Following arthrocentesis and culture, simultaneous empiric antibiotic therapy (based on gram stain) and evacuation of purulent material should be performed. [7]

Further management

Treatment of adults after culture has returned [7][11]

Organism Antibiotics
S. aureus and other gram-positive cocci
Gram-negative cocci
Gram-negative rods
N. gonorrhea
Chlamydia

Treatment of children [10]

Complications

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

  • 1. Chun KC, Kim KM, Chun CH. Infection following total knee arthroplasty. Knee surgery & related research. 2013; 25(3): pp. 93–9. doi: 10.5792/ksrr.2013.25.3.93.
  • 2. Tande AJ, Patel R. Prosthetic joint infection. Clin Microbiol Rev. 2014; 27(2): pp. 302–345. doi: 10.1128/CMR.00111-13.
  • 3. Betts RF, Chapman SW, Penn RL. Reese and Betts' A Practical Approach to Infectious Diseases. Lippincott Williams & Wilkins; 2002.
  • 4. Berry DJ, Lieberman J, Keeney J. Surgery of the Hip. Elsevier Saunders; 2013.
  • 5. Margaretten ME, Kohlwes J, Moore D, Bent S. Does this adult patient have septic arthritis?. JAMA. 2007; 297(13): pp. 1478–1488.
  • 6. Betts RF, Penn RL, Chapman SW. Reese and Betts' a Practical Approach to Infectious Diseases. Philadelphia, PA: Lippincott Williams & Wilkins; 2003.
  • 7. Horowitz DL, Katzap E, Horowitz S, Barilla-LaBarca ML. Approach to Septic Arthritis. Am Fam Physician. 2011; 84(6): pp. 653–660. pmid: 21916390.
  • 8. Bennett JE, Dolin R, Blaser MJ. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Elsevier Saunders; 2015.
  • 9. Mathews CJ, Kingsley G, Field M et al. Management of septic arthritis: a systematic review. Ann Rheum Dis. 2007; 66(4): pp. 440–445. doi: 10.1136/ard.2006.058909.
  • 10. 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): pp. e18–55. doi: 10.1093/cid/ciq146.
  • 11. Kauffman C. Septic Arthritis/Infection Native Joints. https://www.infectiousdiseaseadvisor.com/infectious-diseases/septic-arthritisinfection-native-joints/article/609472/. Updated January 1, 2018. Accessed January 20, 2019.
  • 12. 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.
last updated 11/04/2020
{{uncollapseSections(['OYXI69', '5YXip9', 'LYXwp9', '0QceuX0', '6YXjJ9', 'r2cfQb0', 'qYXCJ9', 'IYXYq9'])}}