Abstract: Objective：To explore a method for measuring patella height in the condition of knee joint effusion.Methods：The imaging data of 50 patients admitted to our hospital from June 2017 to June 2019 were retrospectively analyzed.The conventional Patellar Index and the Modified Patellar Index (MPI) were measured and compared in each patient with or without knee joint effusion.Results：The correlation between MPI and the traditional patella index were evaluated,and the results showed that MPI had a good correlation with the three traditional patella indexes(P<0.05).Assessment of changes in each patella index before and after knee effusion showed that the traditional patella index had significant changes before and after knee joint effusion(P<0.05),while MPI had no significant difference(P＞0.05).Conclusion：The traditional patella index has a significant difference before and after knee joint effusion,while MPI has a good correlation with the traditional patella index.There is no significant change before and after knee joint effusion,so it can be considered to evaluate the patella height under the condition of knee joint effusion.

Key words: knee joint effusion, patella height, patella index