Risk factors and clinical characteristics of deep knee infection in patients with intra-articular injections: A matched retrospective cohort analysis

BackgroundDeep knee infection (DKI), consisting of sepsis arthritis (SA) and chronic low-grade infection (CLGI), is a rare but catastrophic adverse event that can result from intra-articular (IA) injections. The purpose of this study was to assess the risk factors for DKI and describe the clinical characteristics of DKI in patients who received IA injections.MethodsFifty patients with IA injection-induced DKI who underwent surgical treatment between January 2010 and May 2016 served as cases and were matched with non-infected controls who received IA injections in a proportion of 1:5 based on age, gender, and date of admission. All IA injections (both cases and controls) were performed within 6 months of admission at our institution or at a referring institution. Risk factors for injection-induced DKI were analyzed, and the clinical characteristics between SA and CLGI were compared.ResultsThe final multivariate logistic regression analysis demonstrated that body mass index ≥25 kg/m² [odds ratio (OR) = 2.3; 95% confidence interval (CI): 1.1–4.7], corticosteroid injections (OR = 3.21; 95% CI: 1.63–6.31), rheumatoid arthritis (OR = 2.61; 95% CI: 1.20–5.68) and injections performed by general practitioners (OR = 5.23; 95% CI: 2.00–13.67) increased the risk of DKI following IA injections. Of 50 cases, there were 21 SA cases and 29 CLGI cases. SA cases had significantly higher metrics in the categories of fever, local warmth, swelling, rest pain, night pain, limited motion, serum WBC, and CRP levels than CLGI cases.ConclusionsWe identified risk factors and clinical characteristics of injection-induced DKI, which may offer improved guidance on IA injections and knowledge of DKI in patients with IA injections, especially in CLGI patients.