If you were given the choice, and you wanted to reduce human suffering by as much as possible, would you cure blindness or back pain? It seems a silly question. The thought of losing one's sight is, to most people, as frightening as it is depressing: we would no longer be stirred by sunsets or landscapes or the expressions on the faces of our loved ones. Everyday chores would become more difficult, crossing the street perilous. Many sports and pastimes would simply be off-limits, and we would lose a good deal of our independence.
Back pain, on the other hand, is just back pain.
But in fact, it's back pain that causes more misery.