An inflatable soft wearable knee rehabilitation device: Design, fabrication, control and preliminary evaluation

Multiple diseases and injuries can cause knee joint stiffness. Typically, therapists manually move a patient’s lower limb to assist them in regaining range of motion. There are also devices that can be used to aid in the rehabilitation process; however, the majority of them require lengthy rehabilitation sessions or have a fixed axis of rotation that cannot always be aligned with the knee’s moving center of rotation. This work presents the design, fabrication, and evaluation of a soft, inflatable, wearable device without rigid mechanisms that aims to replicate the behavior of the therapist and address the mentioned deficiencies. Two control strategies, passive and assist-as-needed, are defined for the device’s operation. The objective of the passive strategy is to relocate the patient’s knee to the designated position within the specified time. The assist-as-needed strategy, on the other hand, does not interfere if the patient is able to move ahead of the trajectory that the device is following, and only begins to assist when the patient’s limb stops moving. The device underwent experimental testing, and the outcomes were assessed.