Original sentence: It is said that he used a crutch in early youth, but sometimes stubbornly refused it for fear of looking "weak", and had abandoned it entirely by age ten.It is thought that the  withered arm, limp, and crooked back of legend are complete fabrications, but if he did have a disability, it may have been the result of a bout of polio as a small child
Edited sentence: He was a sickly child, and it is likely that the withered arm, limp, and crooked back of legend were the result of a bout of polio at age two or three.It is known that he used a crutch in early youth, although sometimes stubbornly refused it for fear of looking "weak", and he had abandoned it entirely by age ten