Osteomyelitis and Septic Arthritis

The paediatric acute haematogenous form is the focus here. Osteomyelitis is infection within bone, usually seeded through the bloodstream. Septic arthritis is infection in the synovial joint space. In children, the organisms most often identified in these acute infections are Staphylococcus aureus and Kingella kingae. Bone and joint infection can look similar at first because both provoke fever, pain, swelling, and loss of function. The mechanism explains the urgency. Infected bone develops inflammation and oedema in a confined space, which can impair local perfusion and prolong infection. In an infected joint, inflammatory cells and enzymes injure articular cartilage. A child may therefore stop using the limb before the local findings become dramatic. A previously well child with fever who suddenly refuses to walk deserves more than an assumption of a minor injury. A hot, swollen joint with marked pain during passive movement makes septic arthritis especially concerning. Focal bony tenderness with a limp or refusal to bear weight points more toward osteomyelitis, although both conditions can occur together. Septic arthritis is a source-control emergency: obtaining the joint specimen and arranging...