Task-Agnostic Exoskeleton Torque Assistance Reduces Ankle Osteoarthritis Pain: A Pilot Study.

Ankle osteoarthritis (OA) is a chronic joint disorder that causes significant pain and mobility challenges during activities like walking and stair navigation, where high plantarflexor torque demands exacerbate compressive loads on degraded cartilage and subchondral bone. Conventional ankle braces stabilize the joint but often immobilize it, leading to compensatory gait patterns. While powered exoskeletons could alleviate joint stress, many designs are insufficiently backdrivable or versatile to support the volitional motion of OA patients across daily activities. We address these challenges with a lightweight, backdrivable ankle exoskeleton featuring quasi-direct drive actuators and a task-agnostic control framework. This system provides continuous, biomimetic torque assistance for plantarflexion and dorsiflexion, reducing joint loads while preserving natural mobility. In pilot trials with individuals with ankle OA, our device reduced pain and peak joint torque, while improving gait symmetry, stride length, and walking speed. These results highlight the potential of backdrivable ankle exoskeletons as an innovative, non-invasive treatment for ankle OA.