Lot to unpack here....

It sounds like are father's were similar, I didn't know my father had it in his 60's till he told me when in his 80's. I guess they don't like to worry us!

First of all, do you know that it has spread to his legs or are you making that assumption? How bad was the fall etc.. What I'm getting at here is although it may be related, it may not be the primary cause.

One of the things we (PCa patients) have to be concerned about is that some of the medication that we take may cause things like loss of bone density, Someone in their 70's, (guess as a min based on your age) is likely to have some natural loss, then adding the meds a lot of us take may make it a little worse. Also, a femur break, the largest bone in the body, has to be very extremely painful in and of itself.

Having said all that, yes, when it does spread it may often spread to the bones. Although I've mostly heard that it goes to the ribs, spine and hip areas. (again just from reading other's experience in this forum) This is why we often get bone scans when diagnosed, at least I know I did, this was to make sure it hadn't spread. Luckily mine hadn't yet. Folks on here that have had this happen seem to get those "hot spots" radiated when they are found. There are also some drugs that are taken to help the minimize spread and even shrink the cancer.

What's next for him potentially varies greatly depending on a wide range of variables. How advanced was it when diagnosed, what was/is the treatment regimen, etc. etc.. Without knowing a history of his disease, it'd almost be impossible to guess. Add to that, we are mostly patients sharing experiences as opposed to medical folks.

As a piece of free advice, I would think that for you to get any answers you might have to make arrangements to go see your father and try to have a frank discussion with him. Maybe try to get on the list to be in his medical information loop.

Best of luck to both you and your father!