What is the treatment for a septic knee?

Treatment for Septic Knee

The treatment for septic knee requires immediate surgical drainage of the joint (arthroscopy or open arthrotomy) combined with prompt administration of intravenous antibiotics within one hour of diagnosis. 1

Initial Management

• Septic arthritis is considered an orthopedic emergency as bacterial proliferation can rapidly cause cartilage damage 1
• Obtain appropriate microbiologic cultures (joint fluid, blood) before starting antimicrobial therapy, but do not delay antibiotics more than 45 minutes 1
• Administer broad-spectrum IV antibiotics within one hour of diagnosis to cover all likely pathogens 1
• Perform surgical drainage of the joint as soon as possible 1

Surgical Intervention

• Drainage or debridement of the joint space should always be performed 1
• Two main surgical approaches:
  • Arthroscopic drainage - less invasive, better functional outcomes, thorough lavage (average 7L) 2, 3
  • Open arthrotomy - may be preferred for certain cases, particularly MRSA infections 4
• Some patients may require repeated surgical drainage, especially with:
  • Delayed treatment
  • Early unfavorable clinical or biological course
  • Multiresistant organisms 2

Antibiotic Therapy

• Initial empiric antibiotics should include:
  • IV vancomycin (for possible MRSA coverage) 1
  • Consider adding a second agent for gram-negative coverage 1
• Duration of therapy:
  • 3-4 weeks is suggested for uncomplicated septic arthritis 1
  • Longer courses (4-6 weeks) may be needed for patients with slow clinical response 1
• Transition from IV to oral antibiotics can occur when clinical improvement is observed 1

Special Considerations

• For MRSA infections:
  • IV vancomycin is the first-line treatment 1
  • MRSA is an independent risk factor for failure of single washout and may require open surgical treatment rather than arthroscopy 4
• For pediatric patients:
  • IV vancomycin is recommended for acute hematogenous MRSA 1
  • If the patient is stable without ongoing bacteremia, clindamycin can be used as empirical therapy if local resistance rates are low (<10%) 1

Monitoring and Follow-up

• Perform clinical examinations several times per day 1
• Monitor inflammatory markers (ESR, CRP) to guide response to therapy 1
• Early mobilization of the knee once CRP normalizes (average 3 weeks) 2

Pitfalls and Caveats

• Delayed diagnosis and treatment significantly worsen outcomes - each hour delay in antibiotic administration increases mortality 1
• Failure rates of 30-39% have been reported for both medical and surgical approaches 5
• Risk factors for treatment failure include:
  • Advanced age 5
  • MRSA infection 4
  • Elevated synovial WBC count 4
  • Delayed surgical intervention 6
• Functional outcomes are worse with longer time between symptom onset and surgical intervention 6

Treatment Algorithm

1. Obtain joint fluid and blood cultures
2. Start IV antibiotics within 1 hour (vancomycin + gram-negative coverage)
3. Perform surgical drainage (arthroscopy or open arthrotomy)
4. Consider open approach for MRSA infections
5. Continue IV antibiotics for 3-4 weeks
6. Monitor clinical response and inflammatory markers
7. Consider repeat surgical drainage if poor response
8. Transition to oral antibiotics based on culture results and clinical improvement
9. Begin early mobilization when inflammation resolves