A wheelchair is a chair with wheels, used when walking is difficult or impossible due to illness, injury, old age related problems, or disability. These can include spinal cord injuries (paraplegia, hemiplegia, and quadriplegia), broken leg(s), cerebral palsy, brain injury, osteogenesis imperfecta a.k.a. brittle bones, motor neurone disease (MND), multiple sclerosis (MS), muscular dystrophy (MD), spina bifida, and more. Wheelchairs come in a wide variety of formats to meet the specific needs of their users. They may include specialized seating adaptions, individualized controls, and may be specific to particular activities, as seen with sports wheelchairs and beach wheelchairs. The most widely recognized distinction is between powered wheelchairs, where propulsion is provided by batteries and electric motors, and manually propelled wheelchairs, where the propulsive force is provided either by the wheelchair user/occupant pushing the wheelchair by hand ("self-propelled"), by an attendant pushing from the rear using handle(s), or by an attendant pushing from the side use a handle attachment.