Joist connected to wall needs to be replaced
 

A joist on the second floor needs to be replaced/fixed. The problem is that the wall below is connected to the joist. How do I replace the joist without messing with the wall. The main problem is that the wall is in the bathroom and the bathtub and tub surround is connected to the wall. I don't want the wall to move and mess with the structure of the bathtub/tub surround. Any ideas.