Nationwide analysis of adult nongonococcal native septic knee arthritis hospitalizations from 2016 to 2022

BACKGROUND: Septic arthritis (SA) is a medical emergency associated with substantial morbidity and mortality. Although the knee is the most commonly affected joint in adults, contemporary national data describing characteristics, mortality, and healthcare utilization in knee-specific native SA are limited. METHODS: We conducted a retrospective study of adult hospitalizations for nongonococcal native knee SA in the United States using the National Inpatient Sample database from 2016 to 2022. Hospitalizations were identified using ICD-10 diagnostic codes, excluding gonococcal and prosthetic joint infections. Thus, the analytic cohort was restricted to native joint disease and did not include prosthetic joint infection. Weighted analyses were performed to generate national estimates. Multivariable logistic regression was used to identify factors independently associated with in-hospital mortality. RESULTS: Among approximately 205 million adult hospitalizations, 92,290 (0.045%) had native SA of the knee. In-hospital mortality was 2.5%. Patients who died were older, had longer lengths of stay, and incurred more than double the median hospital charges compared with survivors. In multivariable analysis, factors independently associated with higher odds of in-hospital death included respiratory failure (odds ratio [OR] 8.54), sepsis (OR 3.57), liver disease (OR 3.45), cerebrovascular disease (OR 2.27), acute kidney injury (OR 2.05), chronic kidney disease (OR 1.66), myocardial infarction (OR 1.60), heart failure (OR 1.55), and increasing age. Survivors demonstrated substantial postacute care needs, with 36% discharged to skilled nursing or intermediate care facilities. CONCLUSIONS: In this nationally representative cohort, nongonococcal native septic knee arthritis showed substantial in-hospital mortality, morbidity, and healthcare utilization. Mortality was driven primarily by multiorgan dysfunction rather than demographic or socioeconomic factors. Early identification and aggressive management of high-risk patients may improve outcomes.