Clinical algorithms have been developed for septic arthritis The best known is the Kocher criteria for septic arthritis of the hip The risk factors assessed were nonweight bearing on the affected side, ESR >40 mm/hr, fever, and WBC >12,000/mm3 When all four criteria are met, there is a 99% chance that the child has septic arthritis However, the negative predictive value is not as robust; 40% of cases with only 2/4 criteria have a septic joint Management: Prompt surgical intervention is typically advocated for septic arthritis of the hip All children with suspected septic arthritis should be admitted to the hospital for parenteral antibiotics Antistaphylococcal coverage should be initiated in children of any age with suspected septic arthritis The selection of vancomycin over clindamycin depends upon local antibiotic susceptibility patterns, illness severity, and any prior culture results available for the child Coverage should be expanded beyond staphylococcal coverage if the Gram stain demonstrates organisms other than gram-positive cocci in clusters, if gonococcal arthritis is suspected based upon history or cultures from nonjoint sites (e.g., oropharynx, rectum), or in immunocompromised children or children whose arthritis is due to penetrating trauma to the joint In neonates and young infants, ampicillin and a thirdgeneration cephalosporin should be added to augment coverage for GBS and gram-negative rods Standard precautions should be used unless draining lesions exist, in which case contact precautions should be implemented Lyme Disease Arthritis A common cause of septic arthritis in Lyme-endemic regions (northeastern, mid-Atlantic, and Great Lakes states in the United States) is B burgdorferi Lyme arthritis is a monoarticular or pauciarticular (affecting to joints) arthritis that most often affects the large joints, especially the knees, which are involved in over 90% of cases After the knee, the shoulder, ankle, and elbow are the most commonly affected joints It affects approximately 7% of children with Lyme disease The symptoms mimic those of septic arthritis caused by pyogenic organisms (acute bacterial septic arthritis) There are some features that can enable the provider to differentiate the two entities ( e-Table 94.13 ) One clinical prediction rule derived and validated in a Lyme-endemic region showed that children were at low risk for septic arthritis if the ANC was