Septic arthritis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Jumana Nagarwala, M.D., Senior Staff Physician, Department of Emergency Medicine, Henry Ford Hospital; Cafer Zorkun, M.D., Ph.D. [2]
Overview
Septic arthritis is the invasion of the joint space by an infectious agent which produces arthritis. The usual etiology is bacterial, but viral, mycobacterial, and fungal arthritis occur occasionally. Bacteria are either carried by the bloodstream from an infectious focus elsewhere, introduced by a skin lesion that penetrates the joint, or by extension from adjacent tissue (e.g. bone or bursae).
Causes
Septic arthritis develops when bacteria or other tiny disease-causing organisms (microorganisms) spread through the bloodstream to a joint. It may also occur when the joint is directly infected with a microorganism from an injury or during surgery. The most common sites for this type of infection are the knee and hip. Most cases of acute septic arthritis are caused by bacteria such as staphylococcus or streptococcus. Chronic septic arthritis (which is less common) is caused by organisms such as Mycobacterium tuberculosis and Candida albicans.
Diagnosis
History and Symptoms
Septic arthritis should be considered whenever one is assessing a patient with joint pain. Usually only one joint is affected (monoarthritis) however in seeding arthritis, several joints can be affected simultaneously; this is especially the case when the infection is caused by staphylococcus or gonococcus bacteria.
CT
CT is more sensitive than plain films for the detection of early bone destruction and effusion.
MRI
The role of MRI in the diagnosis of septic arthritis has been increasing in recent years in an effort to detect this entity earlier. Findings are usually evident within 24 hours following the onset of infection and include: synovial enhancement, perisynovial edema and joint effusion. Signal abnormalities in the bone marrow can indicate a concomitant osteomyelitis. The sensitivity and specificity of MRI for the detection of septic arthritis has been reported to be 100% and 77% respectively.
Treatment
Medical Therapy
Therapy is usually with intravenous antibiotics, analgesia and washout/aspiration of the joint to dryness.
Primary Prevention
Preventive (prophylactic) antibiotics may be helpful for people at high risk.