In this review of the 1990 septic arthritis literature, we revisit synovial fluid leukocytosis, examine the utility of synovial fluid glucose and protein measurements, and look at the levels of two cytokines, tumor necrosis factor and interleukin-1, in infected joint fluids. We see the many faces of gonococcal arthritis and the ravages of septic arthritis when the host has rheumatoid arthritis. Should we recommend antibiotic prophylaxis for the rheumatoid patient with a prosthetic joint who is undergoing a procedure that leads to transient bacteremia? What are some of the salient features of septic arthritis when it involves the sternoclavicular or sacroiliac joints? We also look at some unusual microorganisms, eg, group C Streptococcus, Streptococcus viridans, Listeria monocytogenes, Pseudomonas cepacia, Pseudomonas maltophilia, and Neisseria sicca. In patients with acquired immunodeficiency syndrome, we encounter reports of septic arthritis, osteomyelitis, and spinal epidural abscess caused by opportunistic microorganisms. Two unusual sites of infection include the C1-2 lateral facet joint and subacromial bursa without involvement of the glenohumeral joint. Finally, we examine how to drain a septic knee: the orthopedic point of view.