A Task-Agnostic Knee Exoskeleton for Reducing Osteoarthritis Pain Across Activities of Daily Life: A Pilot Study

Patellofemoral osteoarthritis is a prevalent musculoskeletal disorder characterized by knee pain during physically demanding activities like stair climbing and sit-to-stand transitions. These movements require high knee extension torques, leading to increased quadriceps activation and patellofemoral joint compression, which aggravates pain. While external torque assistance at the knee joint could theoretically reduce joint loads, traditional exoskeletons have not proven effective in managing osteoarthritis due to their rigid actuation, cumber-some attachments, and inadequate control systems. We address these limitations by modifying a commercial post-operative knee brace with a highly-backdrivable actuator and adapting a task-agnostic torque-assist controller, originally designed for lifting and carrying tasks, to accommodate osteoarthritis patients. In pilot trials with four participants with patellofemoral osteoarthritis, our device facilitated substantial reductions in both pain and perceived difficulty across daily activities including stair/ramp navigation, walking, and sit-to-stand transitions. Across all participants and tasks, pain and difficulty were reduced by 0.82 and 0.57 points, respectively (on a scale of 0 to 4). Electromyography revealed decreased quadriceps activation, varying by participant and task. These preliminary findings motivate future research on backdrivable knee exoskeletons as a novel conservative treatment for patellofemoral osteoarthritis.