CRP and infection: As reported in Fig. 3, with regard to the ‘classical’ combined infection predictors (temperature ≥ 38 °C; WBC ≥ 17 000/mm3 for children < 4 years old and ≥12 000/mm3 for ≥4 years old; ESR ≥ 20 mm/h; and CRP ≥ 10 mg/L), the distribution was not significantly different between SA of the hip and the knee.