Septic arthritis of the hip (SAH) in children is a common pediatric ailment that must be diagnosed immediately as proper treatment is needed to ensure good outcomes. It mostly affects children less than 2 years of age. The causative bacteria depend on age. The most widespread pathogen found at all ages is Staphylococcus aureus (S. aureus), while Kingella kingae (Kk) is most common in children 6 months to 4 years of age. SAH is suspected based on a wide set of clinical, laboratory and radiological (sonography) criteria. MRI is especially useful for diagnosing complications when the child's condition worsens. The diagnosis is only confirmed when joint aspiration finds evidence of bacteria being present. Targeted PCR techniques have largely improved the microbiological diagnosis of Kk. The clinical presentation varies greatly from a limp to prevent weightbearing on the affected leg in a small child with or without fever and very mild to non-existent systemic inflammation, suggestive of SAH due to Kk, to septic shock with quasi-paralysis of the lower limb. Treatment mainly consists of joint drainage and surgical lavage, open or arthroscopic, combined with empirical antibiotic therapy against the likely cause of the infection. A short course of antibiotics is widely used in uncomplicated cases of SAH. The functional prognosis depends highly on the time elapsed before the diagnosis and the start of treatment. Functional sequelae can be severe (growth disturbances, long-term joint damage). LEVEL OF EVIDENCE: Expert opinion.

Keywords: Children; Kingella kingae; Osteoarthritis; Septic arthritis; Staphylococcus aureus.

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