Juvenile rheumatoid arthritis often involves multiple joints and the synovial fluid analysis shows fewer white blood cells and polys. Acute rheumatic fever presents with migratory joint involvement, EKG changes, and elevated ASO titer. Hemophilia will present with an inflamed joint but a bloody effusion. The most difficult differential involves non specific or transient synovitis of the hip. Usually, the onset of symptoms is less acute, there is no systemic illness, it doesn't occur in non walkers, the child is limping but walking, and hip motion is less painful.
Elevated temperature is rare and the sedimentation rate is lower.
Early intervention in septic arthritis is critical not only to relieve the acute symptoms but to preserve joint function. It is well recognized that cartilage can be destroyed by enzymes released by bacteria and also is adversely affected by the products of the inflammatory reaction that occurs to combat the infection. The joint effusion in an infant's hip may mechanically impede the blood supply and cause avascular necrosis of the femoral head if not expeditiously decompressed. Hence the treatment of septic arthritis requires sterilization and decompression of the joint as well as removal of the degradation products and debris of the inflammatory process to halt tissue destruction and preserve the integrity of the joint. Aspiration and irrigation may be used in early infection in an accessible joint that is easily monitored locally and in cases that improve rapidly with such treatment.