Clicking of an artificial joint can have a few causes and most are benign or don’t cause any problems. After a joint is replaced, some clicking or popping may happen as the joint moves. Unless this is causing pain, there shouldn’t be any problem with it.
However, sometimes the clicking is a sign that the joint has moved or dislocated. For this reason, if your mother is having any pain, is unable to bear weight on the hip, or is otherwise uncomfortable, she should see her doctor and have the hip x-rayed to be sure about the cause.