Clinical Characteristics, Imaging Findings and Outcomes in Neonatal Septic Arthritis: A Tertiary NICU Experience

Background: Neonatal septic arthritis is a rare but potentially devastating infection that can present with subtle clinical signs and rapidly progress to joint destruction, osteomyelitis, and permanent sequelae. We aimed to describe the clinical and microbiological characteristics, imaging findings, management, and follow-up outcomes of neonatal septic arthritis patients and to report ultrasonography (US) and magnetic resonance imaging (MRI) findings within the same cohort. Methods: This retrospective observational study was conducted in a tertiary neonatal intensive care unit and included neonates who were diagnosed with septic arthritis between January 2016 and December 2025. Demographic, clinical, laboratory, microbiological, imaging, treatment, and outcome data were systematically obtained from medical records. The diagnosis was based on compatible clinical findings supported by laboratory and/or microbiological evidence, with imaging used to support diagnosis and guide management. Results: Twelve neonates were included. The median gestational age was 36.5 weeks (26–40), and the median birth weight was 2435 g. The median symptom onset was 22 days of life. The hip (n = 4) and knee (n = 4) were most commonly affected. Pseudoparalysis and swelling were the most frequent findings. Synovial cultures were positive in 10/12 (Staphylococcus aureus, n = 7; methicillin-resistant Staphylococcus aureus (MRSA), n = 3), and blood cultures were positive in 6/12. US detected joint effusion in 33% of the patients, whereas MRI revealed inflammatory changes in all the patients. Concomitant osteomyelitis occurred in 5/12 patients. Orthopedic sequelae developed in 6/12; no mortality was observed. Conclusions: Neonatal septic arthritis is associated with a substantial risk of osteomyelitis and early sequelae. Delayed recognition may worsen outcomes. Normal ultrasonographic findings should not exclude the diagnosis when clinical suspicion persists, and MRI may provide complementary information for timely management.