Real-world management of native knee septic arthritis at a university hospital, 2018-2025: A retrospective cohort with comparative surgical outcomes and development of a weighted-incidence syndromic combination antibiogram.

BACKGROUND

The optimal initial management of adult native knee septic arthritis remains debated. We compared outcomes across arthroscopic irrigation and debridement, open arthrotomy, and aspiration-led medical therapy, and developed a locally calibrated Weighted-Incidence Syndromic Combination Antibiogram (WISCA) to guide empiric antibiotics.

METHODS

Single-center retrospective cohort of 136 adults (2018-2025). Index modalities were open arthrotomy (n = 88), arthroscopy (n = 32), and medical therapy (n = 16). Primary outcomes were unplanned reintervention, number of procedures, complications, and hospital length of stay (LOS). Secondary outcomes included conversion to open surgery, knee range of motion, and in-hospital mortality. Multivariable models (bias-reduced logistic for binary endpoints, Poisson/negative-binomial for counts, and Gamma log-link for LOS) adjusted for demographics, comorbidities, and symptom-to-treatment time. WISCA estimated regimen-level empiric coverage using a hierarchical Bayesian model weighted by local pathogen incidence and susceptibility.

RESULTS

Arthroscopy required fewer procedures (median 2.0 vs 2.5) and had shorter LOS (median 5.5 vs 11.5 days) than arthrotomy (both p ≤ 0.002). Adjusted analyses confirmed fewer procedures (incidence rate ratio 0.67, 95 % confidence interval 0.51-0.88) and shorter LOS (ratio of means 0.37, 95 % confidence interval 0.26-0.53) with arthroscopy, without a clear increase in unplanned reintervention. Medical treatment and aspiration had the highest conversion to surgery (37.5 %) and more downstream complications. Longer symptom duration, diabetes, and cirrhosis independently predicted greater procedure burden. The WISCA favored β-lactam-anchored regimens with anti-staphylococcal coverage for most patients and supported initial narrow-spectrum β-lactam choices.

CONCLUSION

In routine care, arthroscopic irrigation and debridement achieves infection control with lower resource use than open arthrotomy and should be the preferred first-line surgical strategy for most presentations. Open arthrotomy remains important for anatomically complex or advanced disease, and aspiration-only strategies should be limited to carefully selected, closely monitored patients. A locally calibrated WISCA can support rational empiric choices and timely de-escalation alongside early source control.