Sonography for the investigation of a child with a limp

Hip pain is a common paediatric presentation and is potentially serious. While hip pain can be attributed to primary hip pathology, the hip area is also a common site for referred pain. This often poses a diagnostic challenge particularly in the young child who may not verbalise the point of pain and may not report an injury. Differential diagnoses for paediatric hip joint pain range from fracture, transient synovitis, septic arthritis with or without osteomyelitis, juvenile idiopathic arthritis (JIA, previously juvenile rheumatoid arthritis JRA), Legg-Calve-Perthes' disease (LCP), slipped capital femoral epiphysis (SCFE) to haemarthrosis in patient with a clotting disorder. Referred pain from abdominal pathology, for example; appendicitis, psoas abscess or haematoma should also be considered. The evaluation and management of hip pain requires a thorough history and physical examination. A radiograph is usually indicated to rule out any bony injury. Septic arthritis is a medical emergency requiring urgent surgical as well as medical treatment. Ultrasound of the hip joint plays a role in helping to differentiate which hips require early intervention and to guide a needle aspiration of joint fluid if indicated. In this article, we aim to review the anatomy of the hip, techniques in ultrasonographic examination and some common pathologies in the paediatric hip.