What is the diagnosis and treatment for septic (infectious) arthritis?

From the Guidelines

Septic arthritis is a medical emergency that requires immediate diagnosis and treatment with joint drainage and appropriate antibiotic therapy to prevent permanent joint damage and improve patient outcomes. The diagnosis of septic arthritis is typically made based on clinical presentation, including a hot, swollen, painful joint with limited range of motion, often accompanied by fever, and confirmed by joint aspiration and culture.

Key Considerations

• The infection typically occurs when bacteria enter the joint space through hematogenous spread, direct inoculation, or contiguous spread from nearby infection 1.
• Risk factors include immunocompromised states, pre-existing joint disease, intravenous drug use, and recent joint procedures.
• Prompt treatment is essential to prevent permanent joint damage, as bacterial toxins and the inflammatory response can rapidly destroy cartilage.

Treatment Approach

• Drainage or debridement of the joint space should always be performed 1, with surgical debridement of the hips recommended for children, whereas arthrocentesis may be adequate for other infected joints 1.
• Initial empiric antibiotics should cover Staphylococcus aureus and streptococci, with vancomycin 15-20 mg/kg IV every 8-12 hours often used for adults until culture results are available 1.
• For children, IV vancomycin is recommended, with clindamycin 10–13 mg/kg/dose IV every 6–8 h as an alternative if the clindamycin resistance rate is low 1.
• Antibiotic therapy should be adjusted based on culture results and continued for a minimum 3–4-week course for septic arthritis, with longer courses needed for complex infections 1.

Rehabilitation and Outcome

• Joint immobilization during the acute phase followed by gradual rehabilitation helps preserve joint function.
• The goal of treatment is to prevent permanent joint damage and improve patient outcomes, with prompt treatment being essential to achieve this goal.

From the Research

Diagnosis of Septic Arthritis

• Septic arthritis must be considered and promptly diagnosed in any patient presenting with acute atraumatic joint pain, swelling, and fever 2
• Risk factors for septic arthritis include age older than 80 years, diabetes mellitus, rheumatoid arthritis, recent joint surgery, hip or knee prosthesis, skin infection, and immunosuppressive medication use 2
• Physical examination findings and serum markers, including erythrocyte sedimentation rate and C-reactive protein, are helpful in the diagnosis but are nonspecific 2
• Synovial fluid studies are required to confirm the diagnosis 2, 3
• Isolation of the causative agent through synovial fluid culture is not only definitive but also essential before selecting antibiotic therapy 3

Treatment of Septic Arthritis

• Empiric antibiotic therapy should be initiated if there is clinical concern for septic arthritis 2
• Oral antibiotics can be given in most cases because they are not inferior to intravenous therapy 2
• Total duration of therapy ranges from two to six weeks; however, certain infections require longer courses 2
• Gram stain results should guide initial antibiotic choice 2, 3
• Vancomycin can be used for gram-positive cocci, ceftriaxone for gram-negative cocci, and ceftazidime for gram-negative rods 3
• Evacuation of purulent material with arthrocentesis or surgical methods is necessary 3
• Management involves a combination of medical and surgical treatments tailored to infection severity, causative pathogens, and overall patient condition 4
• Medical treatment is not inferior to surgical treatment, however, 30% of patients with septic arthritis ultimately require surgical treatment 4
• New therapies are being sought, including the use of antimicrobial peptide or phage therapy 5

Special Considerations

• Special consideration should be given to patients with prosthetic joint infection 3
• In patients with prosthetic joint infection, the intraarticular cutoff values for infection may be as low as 1,100 white blood cells per mm3 with a neutrophil differential of greater than 64 percent 3
• The 90-day mortality rate of knee septic arthritis is 7% in patients 79 years and younger and from 22% to 69% in patients older than 79 years 4