Septic Arthritis - Etiology

Etiology

Bacteria are 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 bovine tb).

Micro-organisms must reach the synovial membrane of a joint. This can happen in any of the following ways:

• dissemination of pathogens via the blood, from abscesses or wound infections, or from an unknown focus
• dissemination from an acute osteomyelitic focus,
• dissemination from adjacent soft tissue infection,
• entry via penetrating trauma
• entry via iatrogenic means.

Bacteria that are commonly found to cause septic arthritis are:

• Staphylococcus aureus - the most common cause in adults
• Streptococci - the second most common cause
• Haemophilus influenzae - was the most common cause in children but is now uncommon in areas where Haemophilus vaccination is practiced
• Neisseria gonorrhoea - in young adults (now thought rare in Western Europe)
• Escherichia coli - in the elderly, IV drug users and the seriously ill
• M. tuberculosis, Salmonella spp. and Brucella spp. - cause septic spinal arthritis

In bacterial infection, Pseudomonas aeruginosa has been found to infect joints, especially in children who have sustained a puncture wound. This bacterium also causes endocarditis.