Abstract:[Objective] To investigate the influence of medial unicompartmental knee arthroplasty (UKA) on knee kinematics. [Methods] A total of 9 patients who were undergoing UKA for medial knee osteoarthritis were included into this study. A biplane X-ray device was used to collect the imaging data during walking before and after the operation, in addition, the three-dimensional model of the bone was established by CT scanning, and the 3D model of the bone was compared with the X-ray. The six-freedom movements between the femur and tibia and the position of the contact center point of the medial and lateral tibial plateau were measured. [Results] Before operation, there was no significant difference in flexion and extension angle between the involved and uninvolved knees (P＞0.05) , but significant dif- ference was found in internal and external varus and rotation and medial compartment contact center (P＜0.05) . After operation, the flexion and extension angle between the involved and uninvolved knees showed no significant difference as well (P＞0.05) , the internal and exter- nal varus and rotation and medial compartment contact center improved significantly (P＜0.05) , and no significant diffeence was found be- tween involved and uninvolved knees (P＞0.05) . The anterior displacement deformity of tibial medial compartment contact center improved significantly in the involved knee, however, significant difference was still noted compared to the uninvolved side (P＜0.05) . [Conclusion] UKA can effectively improve the inherent biomechanical indexes of knee gait cycle, especially in force line and rotation, but there is still a certain forward movement in the contact center of medial compartment.