If you do not use a wheelchair in your waking life and dream that you are in a wheelchair, then it suggests that you need to stop depending on others. A situation or relationship has made you feel helpless. Alternatively, a wheelchair indicates that you are literally letting others push you around. You need to start standing up for yourself.
If someone is able-bodied in real life, but you dream that they are in a wheelchair, then it suggests that he/she is in need of your help. They may be afraid to ask you directly and have been dropping hints which your subconscious may have picked up on.