Objectives To quantitatively assess vascularity changes of acute septic hips in infants using Doppler ultrasonography. To compare these findings with asymptomatic hips, and establish a correlation for accurate diagnosis between these findings. Methods In this prospective case–control study, we included all children under 1 year of age with a diagnosis of acute septic arthritis of the hip in the case group. For the control group, we enrolled apparently healthy, full-term neonates and infants not affected with any hip pathology. Doppler ultrasound of the medial femoral circumflex artery of the hip joint was done using a single Phillips HDI 5000 sonography machine. Following parameters were studied: peak systolic velocity (PSV), resistive index (RI), pulsatility index (PI), and systolic to diastolic ratio (SD ratio). Results Doppler signals and spectral waveforms were obtainable in 100% of hips in both groups. A statistically significant difference was found between the cases and controls with respect to their PSVs, RIs, PIs and SD ratios. The most striking difference was found between the PSVs of the two groups, whose mean was 6.18 in the control group and 11.8 in the case group. No significant correlation between age/gender and any of the 4 parameters was found. Conclusion Doppler parameters are useful in raising suspicion of onset in the diagnosis of septic arthritis. No correlation was found between age or gender and any parameter in control group. These baseline values can be held valid for all children below the age of 7 months.