In the humans the tailbone or the coccyx has really no function as such because it is really remnant of the tail which was supposed to be there in the earlier forms of human existence and that is why the name tailbone.

 Well it may be wrong to say that it is useless because of the fact that a lot of muscles and the ligaments and the tendons are attached to it and that means that it can actually become tough sometimes for the doctors to remove the coccyx or the tailbone when it comes to the people who have the coccyx pain or the tailbone pain. 

Coccyx Anatomy and Structure

At the seat portion where the person sits the coccyx plays an important part what will happen is that in most cases the there is the tripod structure at the center of which is the coccyx. Now when you lean backwards the entire weight of the human body will actually be put on the coccyx. 

The coccyx is formed by the four vertebrae and the anterior surface of the bone is concave and it has three grooves which show as to how the junctions are formed in the various segments. 

Now since the bone sits at a place where the entire weight of the body is shifted it so happens that when you fall chances are that you will have an injured coccyx and it will cause the coccyx pain. When that happens you will need the coccyx seat cushion or the tailbone seat cushion to help you out.