If the problem is contracted tendons, then the legs usually straighten out without assistance, and only the most severe cases require the use of casts or splints. Contracted tendons often occur because of the position of the legs in the womb.
If the abnormality is a bone deformity, then the probability of success is poor even if splints are used. This deformity may occur due to an exposure to poisonous plants, other toxins, or certain viral infections during pregnancy. A veterinarian could probably look at the legs (or take radiographs or X rays) and give you a better idea of how to proceed.
