Septic arthritis is a medical emergency that can lead to significant morbidity and mortality arising from irreversible joint destruction and overwhelming sepsis. The purpose of this prospective study is to present epidemiological, clinical and laboratory findings in adult patients with septic arthritis.

Adult patients treated for septic arthritis at the Department of Infectious Diseases, University Medical Centre Ljubljana, Slovenia, from January 2012 to December 2014, qualified for the present report. The following data were analyzed: age, sex, underlying diseases, previous joint procedure, microbiological diagnostic examinations, causative agents, complications and therapy.

During the study period of three years 94 episodes of septic arthritis were diagnosed. There were 49 (52.1%) females and 45 (47.9%) males, aged 64.5 (18 to 97) years. At the first visit elevated concentration of C-reactive protein was found in 93 (98.9%) patients. The most common affected joint was knee (48.9%), followed by shoulder (20.2%), wrist (12.8%), ankle (7.4%) and others. In 8 (8.5%) patients more than one joint was affected. Risk factors were found in 63 (67%) of study patients. The underlying joint disease (e.g. osteoarthritis, rheumatoid arthritis, gout) was found in 50.8% patients, following by malignancy and immunosuppressive therapy in 28.6%, diabetes mellitus in 14.9%, recent trauma in 12.8%, and prior joint procedure in 9.6% patients.

In 65/94 (69.1%) patients the causative pathogen was demonstrated by blood culture in 35.6%, by synovial fluid culture in 48.8%, and by both methods in 13.8% patients. In patients with proven aetiology Staphylococcus aureus was the most frequent (44.6%) isolated pathogen (only one methicillin resistant), followed by gram-negative bacteria in 30.8%, and Streptococcus spp. in 23.1% patients. In 4/65 (6.2%) patients more than one pathogen was isolated. The patients were treated with antibiotics according to isolated pathogen. In 17 (70.8%) out of 24 patients with complications synovectomia was performed, and adjacent osteomyelitis was found in 9 (37.5%) patients.

Our results show that the foremost risk factor in adult patients with septic arthritis is pre-existing joint disease, knee is the principal target of infection, and the most common isolated pathogen is S. aureus. It was established that prompt recognition, early appropriate antimicrobial and surgical treatment in these patients are critical to ensuring a good prognosis.