These descriptions taken from the National Sports Center for the Disabled - Winter Park, Colorado (http://www.nscd.com) give a basic outline of some of the techniques (that require special equipment) and how they relate to a number of disabilities.
Adaptive or disabled skiing also works for a number of where there is no special equipment required and the skier works with a trained guide or guides. These disabilities include visual impairment, deafness, learning difficulties, ... in fact our aim is to get anyone and everyone skiing regardless of their disability!
Individuals use one ski and two outriggers, which are forearm crutches with ski tips mounted to the bases. Primarily used by people who have one stronger leg. Disabilities might include leg amputations, post-polio or trauma that affects primarily one leg.
Individuals use two skis and outriggers or a walker. A metal "ski bra" or a bungee cord between skis often gives more control to feet and legs. Outriggers and walkers help people with lack of lateral control; inability to walk without assistance of crutches, cane, etc.; tendency to fall forward, walk on toes or lean heavily on crutches or walker; or pronounced backward lean. Disabilities might include cerebral palsy, post polio, spina bifida, arthrogryposis, muscular dystrophy, multiple sclerosis, congenital defect or traumatic injury.
Individuals ski in a rigid seat mounted to two asymmetrically cut skis. Some students use hand-held outriggers, while others ski with fixed outriggers attached to the bi-ski. This equipment provides greater stability than a mono-ski and is used by people who use wheelchairs or ambulate with difficulty using crutches, canes or walkers. Disabilities might include cerebral palsy, brain injuries, multiple sclerosis, muscular dystrophy, spina bifida, spinal cord injury, multiple amputations.
Individuals sit in a molded seat that is mounted to a single ski and use hand-held outriggers. The mono-ski is the most difficult sit-down equipment to use because it requires the greatest balance and strength. It is designed for people with double amputations and spinal cord injuries. Other disabilities might include spina bifida, multiple sclerosis, muscular dystrophy and cerebral palsy.