Objective To expand the application of EOS in orthopedic diagnosis and treatment by comparing EOS and CT in the measurement of tibial tubercle-trochlear groove(TT-TG)distance of patellar dislocation.Methods The clinical and complete imaging data(EOS and CT)of 35 cases of patellar dislocation(dislocation group)and 35 cases of non-patellar dislocation(non-dislocation group)were analyzed retrospectively.Results The age difference between the dislocation group and the non-dislocation group was statistically significant(P＜0.05).The TT-TG distance was measured by EOS in the dislocation group(20.19±1.05)mm and the non-dislocation group(13.33±1.17)mm,and the difference between the two groups was statistically significant(P＜0.05).The TT-TG distance was measured by CT in the dislocation group(21.51±1.11)mm and the non-dislocation group(14.21±1.11)mm,and the difference between the two groups was statistically significant(P＜0.05).Bland-Altman plot showed that only three cases were outside the 95％confidence interval.Conclusion Accurate TT-TG distance can be obtained by using EOS system in imaging evaluation of patients with patellar dislocation,which provides a new measurement method for diagnosis and treatment evaluation of patellar dislocation.