Labs - ESR >20, WBC >12
Blood cultures (40-50% grow out)
Xrays
useful to exclude other cause of joint pain (AP & Frog leg)
possible effusion
Consider:
Ultrasound to evaluate for effusion
CT to evaluate for abscess
useful to exclude other cause of joint pain (AP & Frog leg)
possible effusion
Ultrasound to evaluate for effusion
CT to evaluate for abscess
ESR > 40 mm/hr
WBC > 12,000/microliter
Refusal or inability to weight bear on affected joint
Fever 38.5° C or greater
Septic arthritis of the hip 
Acute rheumatic fever
Hip bursitis
Developmental dysplasia of hip
Avascular necrosis of hip
Femur fracture
Lens dislocation
Juvenile idiopathic arthritis