No, but it always helps to have a basic, healthy level of physical fitness. Studying Jodo is no exception, it is definitely a physical, ‘doing’ activity, not a ‘talking’ one. To start the study of Jodo all you really need is a healthy body and mind. I have met and trained with people who started Jodo at age 17, and 60! Age is really NOT a restriction. People of all ages, women and men, regularly study Jodo.
The body motions and stances of Jodo are natural and do not subject your joints to unusual stresses. 90% of Jodo training takes place standing upright. A few kata start or end on your knees, but these are short and represent a small percentage of the overall curriculum.