Septic Arthritis

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What is Septic Arthritis?

Infective arthritis may represent a direct invasion of joint space by a variety of microorganisms, including a variety of bacteria, viruses, mycobacteria, and fungi. Reactive arthritis, a sterile inflammatory process, may be the consequence of an infectious process located somewhere else in the body. Although any infectious agent may cause arthritis, bacterial pathogens are the most rapidly destructive.

Acute septic arthritis tends to be caused by organisms such as Staphylococcus aureus, Streptococcus pneumoniae and group B streptococcus while chronic septic arthritis (which occurs less frequently) is caused by organisms such as Mycobacterium tuberculosis and Candida albicans. In most instances only a single joint is affected, and the knee and the hip are the most commonly infected joints.

Who gets Septic Arthritis?

Septic arthritis can occur at any age. When considering children, it occurs at a higher rate in those under 3 years of age, with the hip, knee and ankle being the most common joints affected.

From age 3 to adolescence, Septic arthritis is uncommon, at which point incidence will increase again. This is due partly to the incidence of STI based Septic arthritis (such as gonococcal arthritis in females with cervical Gonorrhoea).

Septic arthritis is often seen in the elderly, immunosuppressed and those with chronic inflammatory arthritides (such as rheumatoid arthritis), as these are predisposing conditions.

Predisposing Factors

Risk factors for Septic arthritis include a simultaneous bacterial infection, chronic illness, diseases or medications that operate on suppression of the immune system, intravenous drug abuse, rheumatoid arthritis, sickle cell disease, artificial joints, recent damage to a joint leading to bruising/inflammation, or recent joint arthroscopy or other invasive surgery.