A wheelchair is a wheeled mobility device in which the user sits. The device is propelled either manually (by turning the wheels by the hand) or via various automated systems. Wheelchairs are used by people for whom walking is difficult or impossible due to illness (mental or physical), injury, or disability. People with both sitting and walking disability often need to use a wheelbench. The earliest record of the wheelchair in England dates from the 1670s [Oxford English Dictionary, (2nd Ed.), 1989, Vol. XX., p. 203.], and in continental Europe this technology dates back to the German Renaissance.
A basic standard manual wheelchair incorporates a seat and back, two small front (caster) wheels and two large wheels, one on each side, and a foot rest.
Wheelchairs are often variations on this basic design, but there are many types of wheelchairs, and they are often highly customised for the individual user's needs. The seat size (width and depth), seat-to-floor height, footrests/leg rests, front caster outriggers, adjustable backrests, controls, and many other features can be customized on, or added to, many basic models, while some users, often those with specialised needs, may have wheelchairs custom-built.
Various optional accessories are available, such as anti-tip bars or wheels, safety belts, adjustable backrests, tilt and/or recline features, extra support for limbs or neck, mounts or carrying devices for crutches, walkers or oxygen tanks, drink holders, and clothing protectors.
Experiments have also been made with unusual variant wheels, like the omniwheel or the mecanum wheel. These allow more directional movement options.
The electric wheelchair shown on the right is fitted with Mecanum wheels (sometimes known as Ilon wheels) which give it complete freedom of movement. It can be driven forwards, backwards, sideways, and diagonally, and also turned round on the spot or turned around while moving, all operated from a simple joystick.