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Septic arthritis

Definition and Epidemiology

  • Septic arthritis is the infection of a joint, typically caused by bacteria, but can also be due to fungi or viruses.
  • Commonly affects large joints like the knee and hip, but any joint can be involved.
  • Higher risk in individuals with joint prostheses, rheumatoid arthritis, recent joint surgery, and immunocompromised states.


  • Most commonly caused by Staphylococcus aureus, but other bacteria like Streptococci, and in sexually active individuals, Neisseria gonorrhoeae, can also cause infection.
  • The infection can reach the joint through the bloodstream, from a nearby infection, or directly through trauma or surgical procedures.
  • Bacterial toxins and the body’s inflammatory response lead to joint damage.

Clinical Features

  • Rapid onset of severe joint pain, swelling, redness, and warmth.
  • Reduced range of motion in the affected joint.
  • Fever and systemic symptoms may be present.
  • In gonococcal arthritis, may be associated with dermatitis and tenosynovitis.


  • High clinical suspicion based on symptoms and patient history.
  • Joint aspiration is crucial for diagnosis, showing purulent synovial fluid, high leukocyte count, and positive culture.
  • Blood cultures and other investigations to identify the source of infection.
  • Imaging (X-ray, MRI, ultrasound) to assess joint damage.


  • Immediate empirical antibiotic therapy, later adjusted based on culture results.
  • Antibiotics often given intravenously initially, followed by oral antibiotics.
  • Duration of treatment varies but typically lasts for several weeks.
  • Surgical drainage may be necessary in some cases, especially if there is a large effusion or if the infection is in a prosthetic joint.


  • Rapid joint destruction and irreversible damage if not treated promptly.
  • Potential for osteomyelitis and systemic spread of infection.
  • Septic shock in severe cases.

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