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Septic Arthritis of the Foot

Septic arthritis is a bacterial or fungal infection of the joints of the foot.
General Prevention
  • Appropriate shoe wear and avoidance of going barefoot to prevent puncture wounds
  • Treatment of diabetic or neuropathic ulcers
Risk Factors
  • Previous joint trauma or arthritis
  • Inflammatory arthropathy
  • Diabetes or immunocompromise
  • Skin disease
  • Peripheral vascular disease
  • Intravenous drug abuse
  • Damage to joint cartilage occurs from:
    • Bacterial enzymes and toxins
    • Neutrophil-derived proteases and cytokines
    • Ischemia from impaired oxygen diffusion from synovial fluid in presence of purulence
  • Bacteremia to synovium
  • Trauma or puncture wound with direct joint seeding
  • Iatrogenic seeding after arthroscopy or arthrocentesis
  • Patients with diabetes, peripheral neuropathy, or peripheral vascular disease may develop septic arthritis from direct extension of infected foot ulcers.
Associated Conditions
Signs and Symptoms
  • Warmth and swelling usually are present at the infection site.
  • The affected joint is painful and has decreased ROM.
  • The patient may complain of difficulty in bearing weight on the affected extremity.
  • Systemic symptoms such as fever, chills, and sweats may be present.
Physical Exam
  • Try to localize the affected joint by careful palpation.
  • Note erythema, swelling, and tenderness of the involved joint.
  • Assess joint ROM and pain with passive motion.
  • Aspirate the affected joint.
  • Analyze the synovial fluid from the affected joint for cell count, differential, Gram stain, and urate crystals.
  • Culture synovial fluid and blood.
  • Radiographs may show adjacent osteomyelitis or soft-tissue swelling.
  • CT and MRI show fluid in the joint.
Pathological Findings
  • Infections of the foot joints can arise by adjacent spread, direct inoculation, or hematogenous seeding.
  • The most common organism infecting the joints is Staphylococcus aureus.
  • Haemophilus influenzae infection is seen in children <6 years old.
  • Pseudomonas species may infect foot joints from puncture wounds, particularly through the sole of shoe wear.
  • Gram-positive organisms are the most common cause of septic arthritis in adults.
  • Patients with diabetes, foot ulcers, or peripheral vascular disease are likely to have polymicrobial infections with Gram-negative organisms and anaerobes.
Differential Diagnosis
  • Fracture
  • Soft-tissue abscess
  • Osteomyelitis
  • Gout
  • Tumor
  • Reactive arthritis (formerly Reiter syndrome)
  • Charcot arthropathy
General Measures
  • Acute joint infections can be treated with parenteral antibiotics and repeated aspiration of the affected joint.
  • If purulence does not improve, if effusions continue to form beyond 5-6 days, or if the infection is chronic, the joint should be opened surgically, irrigated, and debrided.
  • In both acute and chronic infections, the patient should be splinted to immobilize the infected joint and should be nonweightbearing on the affected extremity.
Special Therapy
Physical Therapy
  • May assist with recovery of ROM, strength, and gait mechanics after resolution of infection
  • Attempt early ROM to prevent contracture.
First Line
  • Initial antibiotic treatment is selected based on patient risk factors and suspected organism.
  • Antibiotic regimen is refined based on culture results.
  • Acute infections that respond to aspiration and antibiotics may be observed.
    • Repeat aspiration is indicated until effusions resolve.
  • Surgical debridement is indicated for patients with:
    • Sepsis
    • Immunocompromise or systemic disease (e.g., diabetes or rheumatoid arthritis)
    • Chronic infection or delayed presentation
    • Adjacent soft-tissue abscess
    • Infection with necrotizing Streptococcus or Gram-negative species
    • Failure to respond clinically to repeat aspirations
  • Uncomplicated infection of the ankle can be addressed with arthroscopic debridement, whereas other joints of foot typically are treated with open arthrotomy and debridement.
  • Necrotic tissue or associated osteomyelitis also is debrided.
Most infections resolve with aggressive treatment, including antibiotics and surgical debridement.
Progressive infections can require amputation.
Patient Monitoring
The patient should be followed closely, and the joint should be reaspirated as the effusion reaccumulates.
741.00 Septic arthritis
Q: What organism is most commonly involved in septic arthritis?
A: S. aureus.
Q: What are common causes of septic arthritis of the foot?
A: Bacteremic seeding, infection from adjacent foot ulcer, seeding from trauma or puncture wound.
Q: What type of antibiotic regimen is most appropriate for patients with diabetes or foot ulceration?
A: Infections in these patients usually are polymicrobial, so the initial antibiotic regimen should be broad spectrum and include coverage for Gram-positive, Gram-negative, and anaerobic species.

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