To my knowledge two or three successful reimplantations of hands have been carried out. Such reimplantations do not work well mainly because of incomplete healing of the nerves, with consequent poor muscle function. In the leg such a reimplantation will work more poorly than an artificial leg.
A transplantation implies implantation of a limb from another human being. Because of additional problems of rejection, such a procedure will fare even worse.
In the future I think advances with artificial limbs will outstrip successful transplants, so that true transplantations of the leg will be unlikely. (I think!)