Bone and Joint Infections in Children: Septic Arthritis.

The pathological invasion of a joint and subsequent inflammation is known as septic arthritis. The knee and hip are the most frequently involved joints. Staphylococcus aureus is the most common cause of septic arthritis in children. An acute onset of illness with an inflamed painful joint and restricted movements and inability to use joint (pseudoparalysis) clinically indicates septic arthritis. The diagnosis is difficult in a neonate or young child where refusal to feed, crying, discomfort during change of diaper (if hip is involved) or attempted joint movement may be the only findings. Fever and other systemic signs may also be absent in neonates. Septic arthritis is diagnosed clinically, supported by appropriate radiological and laboratory investigations. The peripheral blood white cell count is frequently raised with a predominance of polymorphonuclear cells. The acute phase reactants such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are often markedly raised. Ultrasonography and MRI are preferred investigations in pediatric septic arthritis. Determination of infecting organism in septic arthritis is the key to the correct antibiotic choice, treatment duration and overall management. Joint aspirate and/or blood culture should be obtained before starting antibiotic treatment. Several effective antibiotic regimes are available for managing septic arthritis in children. Presence of large collections, thick pus, joint loculations and pus evacuating into surrounding soft tissues are main indications for surgical drainage. Joint aspiration can be a practical alternative in case the lesion is diagnosed early, with uncomplicated presentations and superficial joints.