We heard from narrations that Imam Ali a.s cried when doing ghusul mayyit of our beloved Lady Fatimah a.s, because only then he knew the extent of her broken ribs. Did not our Imam Ali a.s. as a husband know about Lady Fatimah's injury between the 'incident of the door' and her demise?

It appears from narrations that she would hide that broken part from him. She did not want him to see it so she would not hurt him.