An ankle-foot orthosis (AFO) is an orthosis or brace (usually plastic) that surrounds the ankle and at least part of the foot. AFOs are externally applied and intended to control position and motion of the ankle, compensate for weakness, or correct deformities. AFOs are commonly used in the treatment of disorders affecting muscle function such as stroke, spinal cord injury, muscular dystrophy, cerebral palsy, polio, multiple sclerosis and peripheral neuropathy.