Septic Arthritis Causes and Risk Factors

Common Bacterial Pathogens

• Group B streptococcus is a common pathogen in neonates 1
• Kingella kingae is a common pathogen in children under 4 years of age 1, 2
• Salmonella species are a common pathogen in patients with sickle cell disease 1, 2

Routes of Infection

• Hematogenous seeding is the most common route of infection 1
• Extension from a contiguous focus of infection, such as osteomyelitis, is a possible route of infection 1
• In neonates and infants, septic arthritis may occur secondary to spread of osteomyelitis into the adjacent joint 1

Risk Factors

• Intravenous drug use is a risk factor for septic arthritis 3

Pathophysiology

• Bacterial proliferation within the joint space leads to rapid cartilage damage through direct toxicity and inflammatory response 1

Joint Distribution

• Children under 2 years are more likely to have septic arthritis than osteomyelitis 1
• Children between 2-10 years have slightly more osteomyelitis than septic arthritis 1
• Children from 10-18 years have slightly more septic arthritis than osteomyelitis 1

Clinical Implications

• Septic arthritis is considered an orthopedic emergency due to the rapid cartilage damage that can occur 1, 2

Special Considerations

• Polymicrobial infections may occur, especially in specific clinical scenarios, requiring broader antimicrobial coverage 4, 2
• Concomitant joint and bone infections are common in children and may occur in >50% of cases 1