Evaluation of the Insall-Salvati Ratio Among the Vietnamese Population: Application for Diagnosis of Patellar Malalignment

INTRODUCTION AND PURPOSE: An abnormal patellar position has been proven to be associated with anterior knee pain and several other conditions that affect the patellofemoral joint. The purpose of this study was to determine the incidence of patella alta and patella baja and the applicability of the normal range of the Insall-Salvati ratio in the Vietnamese population. METHODOLOGY: Magnetic resonance imaging (MRI) was used to examine 455 Vietnamese subjects’ knees. The Insall-Salvati ratio—the ratio of patellar ligament length (LL) and patellar length (PL)—was measured using sagittal T1-weighted images. RESULTS: The overall mean LL/PL ratio was 1.02 (standard deviation 0.15). No significant differences in the LL/PL ratio were observed between sexes. The frequencies of patella alta (Insall-Salvati ratio >1.32) and patella baja (Insall-Salvati ratio <0.72) were 0.9% and 2.4%, respectively. CONCLUSION: The Insall-Salvati ratio is applicable to Vietnamese populations in which high flexion activities such as kneeling and sitting cross-legged are customary. According to our measurement, the normal range of the ratio among Vietnamese subjects was 0.72 to 1.32.