Abstract： Objective To investigate the MR image characteristics and clinical significance of focal periphyseal edema (FOPE) zone of the adolescent knee which was with or without trauma history,and provide the basis for the correct diagnosis and treatment.Method A total of 12 patients (9 boys,age range 12-16 years,average age 14 years old,3 girls,age range 12-15 years,average age 13 years)who had pain of the knee without the traumatic history and 16 patients (12 boys,age range 10-15 years,average age 14 years;4 girls,age range 11-13 years,average age 12 years) who were painful in the knee after trauma were included in this study.The knee MR examinations were performed in all the patients.The characteristics of MRI between painful knee without trauma and painful knee after trauma were compared and analyzed,and the average vertical distances from the farthest of the edema area to the epiphyseal plate were measured.The vertical distances were measured respectively in sagittal view and coronal view in PD-FS and in sagittal view in T1WI,and the average for the three were calculated.At last,the images with the results of operation or follow-up examinations were compared and confirmed by double blind method.Results The MRI characteristics of FOPE zone in the 12 adolescent who complained painful knee but had no trauma showed low signal intensity in T1WI and high signal intensity in PD-FS.The edema centered at the physis and extended into both the adjacent epiphysis and metaphysic.In addition,it shaped like patches and thread,and edema range (14.5 ± 6.6) mm.The MRI findings of the 16 adolescent had pain of the knee after injury characterized by a wide range of low T1WI signal intensity and increased PD-FS signal intensity involving the articular surface of the epiphysis.The range of edema was (26.2 ± 8.8) mm.There was statistically significant difference between non-traumatic edema and the edema caused by trauma (t =4.346,P ＜0.05).Conclusion A FOPE zone of the adolescent knee is likely to be related to pain in the adolescent growth period and physiologic physeal fusion,and should not be mistaken for an abnormality,while the larger range of edema surrounding the epiphyseal plate may be associated with the trauma of the knee.