Septic Arthritis

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Septic arthritis is an infection in a joint, leading to inflammation, pain, and potential joint damage. It is a medical emergency that requires prompt diagnosis and treatment to prevent joint destruction and other serious complications.

Aetiology

Septic arthritis is typically caused by bacterial infections, but it can also result from viral, fungal, or mycobacterial infections. The most common causative organisms include:

• Staphylococcus aureus (including MRSA)
• Streptococci
• Neisseria gonorrhoeae (particularly in sexually active young adults)
• Gram-negative bacilli (more common in immunocompromised individuals)

Pathophysiology

The pathophysiology of septic arthritis involves:

• Entry of pathogens into the joint space through haematogenous spread, direct inoculation, or contiguous spread from adjacent infected tissues.
• Inflammatory response within the joint, leading to synovial membrane hyperplasia, increased synovial fluid production, and infiltration of neutrophils.
• Release of inflammatory cytokines and enzymes, causing cartilage destruction and joint damage.

Risk Factors

• Age (very young or elderly)
• Pre-existing joint disease (e.g., rheumatoid arthritis, osteoarthritis)
• Joint prostheses or previous joint surgery
• Immunosuppression (e.g., diabetes, HIV, immunosuppressive medications)
• Intravenous drug use
• Recent joint injury or injection
• Sexually active individuals (increased risk of gonococcal arthritis)

Signs and Symptoms

The signs and symptoms of septic arthritis include:

• Severe joint pain, typically affecting a single joint
• Swelling and redness over the affected joint
• Warmth and tenderness of the joint
• Fever and chills
• Limited range of motion
• Systemic symptoms in severe cases (e.g., malaise, weakness)

Investigations

Specific investigations to diagnose septic arthritis include:

• Joint aspiration: Synovial fluid analysis to identify the causative organism through Gram stain, culture, and sensitivity testing.
• Blood cultures: To detect bacteraemia and identify the pathogen.
• Full blood count (FBC): To check for elevated white blood cell count and other markers of infection.
• Inflammatory markers: Elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR).
• Imaging studies:
  • X-rays: To identify joint effusion and rule out other causes of joint pain.
  • Ultrasound: To detect joint effusion and guide aspiration.
  • MRI: To assess the extent of joint involvement and detect osteomyelitis or abscesses.

Management

Primary Care Management

• Early recognition and referral: Prompt referral to secondary care for further evaluation and management.
• Pain management: Analgesics such as paracetamol or NSAIDs for pain relief.
• Immobilisation: Splinting the affected joint to reduce pain and prevent further damage.

Specialist Management

• Empirical antibiotic therapy: Initiation of broad-spectrum intravenous antibiotics until culture results are available. Common choices include vancomycin and ceftriaxone.
• Targeted antibiotic therapy: Adjusting antibiotics based on culture and sensitivity results.
• Joint drainage:
  • Needle aspiration: Repeated as necessary to remove infected synovial fluid.
  • Arthroscopic lavage: Minimally invasive surgical irrigation of the joint.
  • Open surgical drainage: In severe cases or when other methods are ineffective.
• Monitoring and supportive care: Regular monitoring for response to treatment and potential complications. Supportive care may include fluids, nutrition, and physiotherapy to restore joint function.

References

1. NHS (2024) Septic Arthritis. Available at: https://www.nhs.uk/conditions/septic-arthritis/ (Accessed: 24 June 2024).
2. National Institute for Health and Care Excellence (2024) Septic arthritis (acute): antimicrobial prescribing. Available at: https://www.nice.org.uk/guidance/ng65 (Accessed: 24 June 2024).
3. British Medical Journal (2024) Septic arthritis: clinical features, diagnosis, and management. Available at: https://www.bmj.com/content/350/bmj.h2335 (Accessed: 24 June 2024).
4. Matthews, P.C., et al. (2020) 'Septic arthritis: current diagnostic and therapeutic algorithm', Current Rheumatology Reports, 22(7), pp. 1-11.

Back to Top