A condition in which bones become porous and lose their strength is_.

   Osteoporosis is a bone disease that occurs when the body loses too much bone, makes too little bone, or both. As a result, bones become weak and may break from a fall or, in serious cases, from sneezing or minor bumps. Osteoporosis means “porous bone.” Viewed under a microscope, healthy bone looks like a honeycomb.

Explanation:

osteoporosis is the answer