A 2 degree of freedom (DOF) inner skeleton robot (i.e. power assisted artificial joint) that is designed to assist human elbow flexion-extension motion and forearm supination-pronation motion for daily life activities is proposed. This paper presents a prototype of inner skeleton robot that is supposed to assist the motion from inside the human body for the elderly or physically disabled persons and acts as an actuated artificial joint. The proposed system is controlled based on the activation patterns of the muscles electromyogram signals by applying an effective fuzzy-neuro control method. We have developed an actuator and introduce a T-mechanism for the proposed system. The proposed system can be expected to be an artificial joint for the future generation. The effectiveness of the proposed system has been evaluated by experiment.