Comparison of clinical and biological data between septic arthritis of the hip and those of the knee caused by Kingella kingae.

Kingella kingae is the leading cause of osteoarticular infections in children under 4 years, with septic arthritis (SA) being the most common manifestation. The present study aimed to define the clinical and biological characteristics of SA of the hip and of the knee caused by K. kingae , and, secondarily, identify whether there were significant differences between them; this with the objective to assess if different possible strategies of diagnosis and treatment could be applied to different joints. Medical records of 100 children (50 hips, 50 knees) with confirmed K. kingae SA were analyzed, including sex, age, temperature, white blood cell (WBC) count, platelet count, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR). Children with hip SA had a significantly higher proportion of fever ≥38.5 °C (42% vs. 14%, P < 0.05) and higher median CRP levels (32.0 vs. 21.0 mg/L, P < 0.05) compared with those with knee SA. No significant differences were found in WBC count, ESR, or platelet count. These findings suggest that hip SA presents with more pronounced systemic inflammation (higher fever and CRP) than knee SA. Further research is needed to assess whether SA in other joints (e.g. ankle, wrist, and shoulder) also exhibits distinct clinical and biological patterns. This study highlights potential differences in K. kingae SA presentation based on joint involvement, which may influence clinical management. Further studies seem essential to understand whether SA affecting other joints (e.g. ankle, wrist, and shoulder) also results in specific clinical and biological presentations.