TABLE 60.2 COMMON CAUSES OF JOINT PAIN Septic arthritis (bacterial) Osteomyelitis Kawasaki disease Lyme disease Transient synovitis Postinfectious (reactive) Traumatic Serum sickness Henoch–Schönlein purpura Trauma A key initial point in the history is whether trauma preceded the pain A radiograph will detect fractures or a slipped capital femoral epiphysis (SCFE) Classically, an SCFE occurs in the obese adolescent with hip or knee pain (Chapters 111 Musculoskeletal Trauma and 121 Musculoskeletal Emergencies ) Importantly, only about half of children will report preceding trauma and there may be bilateral disease in about one-third of children Plain radiographs (including the frog-leg view of the hip) showing a widened epiphysis and caudal displacement of the femoral head establish the diagnosis TABLE 60.3 LIFE-THREATENING CAUSES OF JOINT PAIN Acute rheumatic fever Kawasaki disease Malignancy Leukemia Neuroblastoma Bone tumor