First let me define handicapped and disabled. Handicapped is when you can't do something in the normal manner but you can still do it. Disabled is when you can't do one or many things no matter how much you try or how much you want to. RSD causes severe changes in muscles and many people suffer from spasms and myclonic jerks. These can cause a steady hand to spill water, draw unwanted lines when writing, drop things and stop all activity.
Severe spasms causes pain that requires attention to be drawn away from everything else.
In a leg, spasms can cause a fall. Besides spasms, many muscles can become atrophied. Sometimes when RSD causes many severe spasms, the muscles may become very hard and strong rather than atrophied. The result of these types of spasms is a strong but uncordinated limb. Many unknowing persons may question whether a RSD patient cannot do things because they believe that the patient is active even though the spasms make it impossible to do many normal things.