Suppurative arthritis may result from seeding of the joint during bacteremia. Other routes include spread from an adjacent site of infection and direct inoculation. Infecting organisms include gonococci, Staphylococcus, Streptococcus, H. influen-zae, and gram-negative bacilli.
Suppurative arthritis causes a tender, painful, swollen, and erythematous joint. Large joints (knee, hip, shoulder) are most often infected, and the arthritis is usually monoarticular. Joint aspiration shows cloudy synovial fluid that clots readily and has a high neutrophil count. Gram stain and culture are positive in 50–70% of cases. Treatment is rapid intervention with antibiotics to prevent permanent joint damage.
Lyme disease is caused by the spirochete Borrelia burgdorferi. The disease is arthro-pod-borne, spread by deer ticks (Ixodes dammini). Symptoms are skin rash (ery-thema chronicum migrans), and migratory arthritis involving the knees, shoulders, and elbows. The histology of the arthritic joint is similar to RA. Lyme disease can also have CNS and cardiac involvement. Serologic tests may remain negative until infection has been present for several weeks.