Septic arthritis
A medical emergency, septic (infectious) arthritis is caused by bacterial invasion of a joint, resulting in inflammation of the synovial lining. If the organisms enter the joint cavity, effusion and pyogenesis follow, with eventual destruction of bone and cartilage.
Septic arthritis can lead to ankylosis and even fatal septicemia. However, prompt antibiotic therapy and joint aspiration or drainage cures most patients.
Causes
In most cases of septic arthritis, bacteria spread from a primary site of infection, usually in adjacent bone or soft tissue, through the bloodstream to the joint.
Common infecting organisms include four strains of gram-positive cocci—Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, and Streptococcus viridans—and two strains of gram-negative cocci—Neisseria gonorrhoeae and Haemophilus influenzae. Various gram-negative bacilli—Escherichia coli, Salmonella, and Pseudomonas, for example—also cause infection.
Anaerobic organisms such as gram-positive cocci usually infect adults and children older than age 2. H. influenzae most often infects children younger than age 2.
Risk factors
Various factors can predispose a person to septic arthritis. Any concurrent bacterial infection (of the genitourinary or the upper respiratory tract, for example) or serious chronic illness (such as cancer, renal failure, rheumatoid arthritis, systemic lupus erythematosus, diabetes, or cirrhosis) heightens susceptibility. Consequently, alcoholics
and elderly people run a higher risk of developing septic arthritis.
and elderly people run a higher risk of developing septic arthritis.
Of course, susceptibility increases with diseases that depress the autoimmune system or with prior immunosuppressant therapy. I.V. drug abuse (by heroin addicts, for example) can also cause septic arthritis.
Other predisposing factors include recent articular trauma, joint surgery, intra-articular injections, and local joint abnormalities.
Signs and symptoms
Acute septic arthritis begins abruptly, causing intense pain, inflammation, and swelling of the affected joint, with low-grade fever. Although it usually affects a single, large joint, it can affect any joint, including the spine and small peripheral joints.
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