In the current study, we formulated ontological descriptions for emotional states of users using motion assistance apparatus. In our previous studies, we developed apparatus that assists the ankle joints of patients in neuro-rehabilitation. Although we have confirmed the apparatus can improve the gait of the patient while walking, we have to capture and manage patients’ emotions as feedback of the usage. The ontological descriptions provide a feasible framework for common understanding while sharing and using this knowledge. In future work, we will develop a subset of this framework for more practical usage, in addition to expanding the descriptions of emotional states. After that, we will assess the validity and utility for design and implementation of software and hardware applications using this subset.