Ascending stairs is a critical activity in maintaining independence in daily living. The loss of the ankle joint following the transtibial amputation inevitably causes the between-limb asymmetry and poses a great challenge of ascending stairs. The project will identify the asymmetric parameters in stair ascend based on MSK modelling and in addition, investigate the relationship between the temporal/spatial asymmetry and the loading asymmetry. The understanding of the biomechanics factors and their contributions to the stair asymmetry will help to focus on the rehabilitation targets for transtibial amputees.