I have realplayer 11 but a program I want to watch needs 10.5 what do I do?

Have you tried playing it with Version 11? Usually the updated version can still play the older files; the website may have not updated their content to say you can use version 11.

Ty. Tried it. 11 won't work. And it won't dl 10.5 tag.

That's very odd. Version 11 should be backward compatible and able to read all formats of previous versions. What's the file type you are trying to play?

A video on complete knee replacement

What file type is the video?