Osteoarticular infections in paediatric patients are associated with significant morbidity. Pyogenic sacroiliitis is rare and accounts for approximately 1-2% of osteoarticular infections in children. Diagnosis of this disease has been difficult in the past due to its deep location and may be delayed due to the lack of specific clinical signs and symptoms. We identified 11 paediatric patients with clinical-radiological signs of pyogenic sacroiliitis during an 8-year period and observed an unusual cluster of four cases during the last 11 months. Early diagnosis was possible due to a reproducible clinical pattern as well as radiological evidences of infection using magnetic resonance imaging and/or bone scintigraphy; most patients having predisposing factors. Staphylococcus aureus was the sole causative agent identified. All patients including two children with associated muscle abscesses were managed conservatively with antibiotic therapy only and showed good clinical response with no sequelae during follow-up. An algorithm for the correct and prompt diagnosis of this pathology is proposed. Standardised optimal therapy remains to be defined.