If a person is a walker & walks all the time can they have osteoporosis in the foot anyway since it is said walking strengthens the bones?

Walking is a good exercise, which helps to increase bone density ,thus reducing osteoporosis. But overenthusiastic walking may precipitate wear and tear of the joints, Hence keep the walking in moderation.

If there is a question of osteoporosis or even osteopenia at your age, it would be prudent to obtain a rheumatological consultation and likely undergo a DEXA scan. Walking is a terrific exercise but the value is accrued over the years and will provide solely minor benefit on its own if osteoporosis is already present.