A wheelchair is a chair with wheels, designed to be a replacement for walking. The device comes in variations where it is propelled by motors or by the seated occupant turning the rear wheels by hand. Often there are handles behind the seat for someone else to do the pushing. wheelchairs are used by people for whom walking is difficult or impossible due to illness (physiological or physical), injury, or disability .
Manual wheelchairs are those that require human power to move them. Many manual wheelchairs can be folded for storage or placement into a vehicle, although modern wheelchairs are just as likely to be rigid framed.
Manual or self-propelled wheelchairs are propelled by the occupant, usually by turning the large rear wheels, from 20-26 inches (51-66 cm)in average diameter, and resembling bicycle wheels. The user moves the chair by pushing on the handrims, which are made of circular tubing attached to the outside of the large wheels. The handrims have a diameter that is slightly less than that of the rear wheels. Skilled users can control speed and turning and often learn to balance the chair on its rear wheels - do a wheelie. The wheelie is not just for show - a rider who can control the chair in this manner can climb and descend curbs and move over small obstacles.
Foot propulsion of the wheelchair by the occupant is also common for patients who have limited hand movement capabilities or simply do not wish to use their hands for propulsion. Foot propulsion also allows patients to exercise their legs to increase blood flow and limit further disability.
One-arm drive enables a user to guide and propel a wheelchair from one side. Two handrims, one smaller than the other, are located on one side of the chair, left or right. On most models the outer, or smaller rim, is connected to the opposite wheel by a folding axle. When both handrims are grasped together, the chair may be propelled forward or backward in a straight line. When either handrim is moved independently, the chair will turn left or right in response to the handrim used. Another alternative is a LeverDrive chair that propels the chair forwards by using a lever that is pumped back and forth. Some chairs are also configured to allow the occupant to propel using one or both feet instead of using the rims.
Attendant-propelled chairs (or transport wheelchairs) are designed to be propelled by an attendant using the handles, and thus the back wheels are rimless and often smaller. These chairs are often used as 'transfer chairs' to move a patient when a better alternative is unavailable, possibly within a hospital, as a temporary option, or in areas where a user's standard chair is unavailable. These chairs are commonly seen in airports. Special airplane transfer chairs are available on most airlines, designed to fit narrow airplane aisles and transfer wheelchair-using passengers to and from their seats on the plane.
Wheelbase chairs are wheeled platforms with specially moulded seating systems interfaced with them for users with a more complicated posture . A molded seating system involves taking a cast of a person's best achievable seated position and then either carving the shape from memory foam or forming a plastic mesh around it. This seat is then covered, framed, and attached to a wheelbase.
Light weight and high cost are related in the manual wheelchairs market. At the low-cost end, heavy, tubular steel chairs with sling seats and little adaptability dominate. Users may be temporarily disabled, or using such a chair as a loaner, or simply unable to afford better. Heavy unmodified manual chairs are common as "loaners" at large facilities such as airports, amusement parks and shopping centers. In a higher price range, and more commonly used by persons with long-term disabilities, are major manufacturer lightweight chairs with more options. The high end of the market contains ultra-light models, extensive seating options and accessories, all-terrain features, and so forth. Reclining wheelchairs have handbrake-like controls attached to the push handles or posts supporting the backrest which, when pressed by the caregiver, allow the backrest to recline from is normal upright position (at 90 degrees) to varying angles up to 180 degrees.
An electric-powered wheelchair is a wheelchair that is moved via the means of an electric motor and navigational controls, usually a small joystick mounted on the armrest, rather than manual power. For users who cannot manage a manual joystick, headswitches, chin-operated joysticks, sip-and-puff or other specialist controls may allow independent operation of the wheelchair