fractures and nursemaid’s elbow, as well as with contusions and other minor soft tissue injuries (see also Chapter 111 Musculoskeletal Trauma ) The diagnosis of trauma must be considered even in the absence of known history of injury in preverbal children, as events may have been unwitnessed Caregivers are also unlikely to be forthcoming about intentionally inflicted injuries Careful physical examination of the child often identifies other signs of nonaccidental trauma In addition, inflicted fractures may have characteristic findings on radiographs Identifying such injuries is crucial to preventing further, potentially more serious injuries Children with hemophilia or other bleeding disorders may have hemarthrosis or hematoma with minimal or no trauma The affected joint is swollen and tender with limited range of motion but there is typically no fever or other systemic symptoms Although much less common than trauma, infection may also cause decreased use of an arm There may be a history of fever, and onset of arm disuse is often less abrupt than with trauma The infection can be located at any point from the shoulder to finger and may be superficial (e.g., cellulitis, paronychia) or deep Arthritis and osteomyelitis frequently have associated localized swelling, warmth, and tenderness; infected joints usually have limited, painful range of motion With more severe infections (e.g., those with associated bacteremia), the child may be febrile and appear ill Laboratory findings may include elevated white blood cell count (WBC), sedimentation rate (ESR), or C-reactive protein (CRP) level Blood culture results may yield the offending agent Acutely, radiographs are often nondiagnostic; if arthritis or osteomyelitis is suspected, ultrasound, bone scintigraphy, or magnetic resonance imaging (MRI) should be considered (depending on the clinical scenario), with arthrocentesis or subperiosteal/bone aspiration as indicated (see Chapters 94 Infectious Disease Emergencies and 121 Musculoskeletal Emergencies ) Congenital syphilis, although rare, may present as pseudoparalysis in infants due to metaphysitis, periostitis, osteochondritis, or pathologic fracture, with bony changes evident on the radiograph (pseudoparalysis of Parrot) In addition to bone or joint infections described above, one must keep in mind that soft tissue infections may also lead to decreased arm use These include cellulitis, myositis/pyomyositis, and necrotizing fasciitis Necrotizing soft tissue infections in children are most commonly caused by group A Streptococcus; other agents include Staphylococcus aureus and anaerobic organisms Predisposing factors include skin trauma (e.g., laceration, burn, surgery) and varicella, although the skin may be intact Children are usually febrile and the